SIG MCX review

[LittleLebowski]

Very technical, good review.

http://www.recoilweb.com/recoil-exclusive-breakdown-of-the-sig-mcx-56367.html

[Byron]

Aw, you got my hopes up. MCX not MPX.


But still a cool review!

This part confused me though:

I would seriously consider this lower with [I]any upper.

While I agree the features/controls look great on that lower, I don't understand how you'd use it with any upper besides an MCX, based on photo 12.

[LittleLebowski]

Title edited.

[Wyoming Shooter]

I just purchased a Sig MCX Patrol. I now have only about 100 rounds through the gun so these are very early thoughts.

My cost at Rocky Mountain Discount Sports in Sheridan, WY was $1700. I mounted a Vortex Sparc II, Magpul MBUS, and Blue Force VCAS. This is a light carbine. Weight, with accessories described, is 7.91 lbs. unloaded. Weight with loaded 30-round Magpul PMAG is 8.95 lbs. The folding telescoping stock has LOP range from 11" - 13". Length with stock fully extended is 35.5". Length with stock folded is 27".

I zeroed at 50 yards with no issues. The Sparc II and MBUS co-witness if that's important to you. With my crappy blasting ammo, the gun is shooting about 1 MOA braced on my range bag. The trigger is abysmal. It will be replaced, soon. I had no malfunctions of any sort in the first 100 rounds. I intend to mount a Thunder Beast flash hider which will allow me to run my TB 30CB9.

While it is way too early to draw any conclusions, my first impression is favorable. I will follow-up with additional info after further use. From the Big Empty, ELN.

https://www.sigsauer.com/store/sig-mcx-patrol.html

http://www.vortexoptics.com/category/sparc_II_red_dot

https://www.magpul.com/products/firearms-accessories/mbus-sights

https://www.blueforcegear.com/vickers-sling

https://thunderbeastarms.com/products/cb-flash-hider

[GJM]

Ed, hopefully they are more durable than the MPX. I have three, my friends another half dozen, all used in USPSA. Soft shooters, but still a work in process as to small parts issues.

[call_me_ski]

Ed, hopefully they are more durable than the MPX. I have three, my friends another half dozen, all used in USPSA. Soft shooters, but still a work in process as to small parts issues.

I traded away my MCX after I was on charging handle number 3 before I hit 500 rounds. They have a new charging handle but they still ship the rifles with the original one that fails easily. They only send you the new one if you break the first.

I wanted the like the gun but it seems like Sig got 95% of the way there and stopped trying.

[Sensei]

So, I'm a fan of the MCX when in its intended configuration as a 300blk SBR. Here is mine:
16835

Without the suppressor, the minimum folded length is just 20". That is 4" smaller than my 9" BMC upper on a CMT UMP-PDW that I reviewed here:

https://pistol-forum.com/archive/index.php/t-22028.html

It produces 1" groups at 50 yards using an Aimpoint T2 and Barnes 110 grain VOR-TX (TAC-TX black tips) and is reliable with 1200 rounds in this SBR configuration.

For those of you who plan to replace the factory trigger - be careful. There are multiple bolt carrier assemblies out there, and not all are are compatible with after market triggers. The new "G" marked carriers with a firing pin safety will work with the Geissele SSA. The ALG ACT and stock trigger will function in the "non-G marked" carriers. Others may be hit or miss.

[Wyoming Shooter]

According to Mike Chandler at Sig, my carbine is not subject to the recall and has the most recent charging handle. I'll send some additional rounds down range and post more.

[MSparks909]

So, I'm a fan of the MCX when in its intended configuration as a 300blk SBR. Here is mine:
16835

Without the suppressor, the minimum folded length is just 20". That is 4" smaller than my 9" BMC upper on a CMT UMP-PDW that I reviewed here:

https://pistol-forum.com/archive/index.php/t-22028.html

It produces 1" groups at 50 yards using an Aimpoint T2 and Barnes 110 grain VOR-TX (TAC-TX black tips) and is reliable with 1200 rounds in this SBR configuration.

For those of you who plan to replace the factory trigger - be careful. There are multiple bolt carrier assemblies out there, and not all are are compatible with after market triggers. The new "G" marked carriers with a firing pin safety will work with the Geissele SSA. The ALG ACT and stock trigger will function in the "non-G marked" carriers. Others may be hit or miss.

Is the "G" carrier something that Sig is going to standardize on in the future? I plan to pick up a MCX later down the road. I'm glad I waited as it seems there's been a few bugs to work out. But I do like the idea of the platform, especially in the 300 BLK SBR configuration.

[Sensei]

Is the "G" carrier something that Sig is going to standardize on in the future? I plan to pick up a MCX later down the road. I'm glad I waited as it seems there's been a few bugs to work out. But I do like the idea of the platform, especially in the 300 BLK SBR configuration.

One would think that the "G" marked FPS will become the standard since is has the proper geometry to function with the ALG, SSA, and stock triggers (according to the internet), while the "non-G" FPS only works with the ALG and stock trigger. However, trying to predict Sig's business practices can be tough.

[Trigger]

On the firing pin safety issue, it was in part a fix for a non-problem. The bolt carrier is light enough that if you drop the bolt on a manually chambered round (one not stripped out of the magazine, but dropped manually into the chamber) there is a chance it could slam fire. So Sig redesigned the carrier, added a firing pin retaining spring, lightened the firing pin, and added a hammer-activated firing pin stop. The firing pin stop is not compatible with lightened or match hammers. The stock MCX has a lousy trigger, and desperately needs an aftermarket trigger.

Since all this was done to fix a non-problem, the first solution is to not drop the bolt on a manually chambered round. The next would be to install the upgraded bolt carrier, but remove the firing pin stop while retaining the firing pin spring. This will allow the MCX to use better triggers+hammers than stock. The new firing pin stop is also a device that might make the rifle less reliable or prone to malfunction. I'm not convinced that it is reliable.

YMMV.

[Wyoming Shooter]

My rifle shipped with the "new" bolt carrier, firing pin stop, and charging handle. The factory trigger is dreadful. I spoke with Michael Chandler at SIG about replacing it with a Geissele SSA. Mr. Chandler informed me that SIG is now selling its own replacement trigger - the "Sig Sauer Match Grade AR Trigger Kit" for $114. He claims it's very similar to the Geissele. I asked him if it was manufactured by Geissele and didn't get a definitive response. It wouldn't surprise me. The Sig trigger is about half the cost of the Geissele. I ordered the Sig trigger. I was told it will arrive in about 3 weeks. I'll keep y'all posted.

[Wyoming Shooter]

I ordered a Sig factory replacement trigger on 05/26/17. Total cost was $114. The trigger arrived 06/10/17. The packaging indicates "Made in United States" but does not designate the manufacturer. Replacing the MCX trigger is much like replacing a standard AR trigger. If you've not replaced an AR trigger before, I encourage you to watch some instructional videos or have a smith do the work. The new trigger is much smoother and lighter. My trigger scale indicates an average break of 4 lbs 15 oz. Range testing to follow. From the Big Empty, ELN.

[Sensei]

Of note, today I tried the purple hammer spring that came with my ALG ACT trigger. This lighter spring would was producing light primer strikes every third round or so with Barnes TAC-TX. The mil-spec hammer spring works flawlessly.

[MSparks909]

I ordered a Sig factory replacement trigger on 05/26/17. Total cost was $114. The trigger arrived 06/10/17. The packaging indicates "Made in United States" but does not designate the manufacturer. Replacing the MCX trigger is much like replacing a standard AR trigger. If you've not replaced an AR trigger before, I encourage you to watch some instructional videos or have a smith do the work. The new trigger is much smoother and lighter. My trigger scale indicates an average break of 4 lbs 15 oz. Range testing to follow. From the Big Empty, ELN.

2 stage or single stage?

[Wyoming Shooter]

2 stage or single stage?

It's a two stage.

[Sensei]

Another 20 rounds of Barnes TAC-TX and 60 rounds of Remington 120 grain were fired today with the ALG ACT installed. Half of those rounds were with a SiCo Omega. No issues with the light primer strikes that were occurring with the purple hammer spring, and the rifle ran 100% both suppressed and unsuppressed.

Trigger weight with the gray, mil spec hammer spring is right at 6 lbs - not too shabby. The standard factory trigger was 9 lbs in my rifle.
Wyoming Shooter, are you able to measure the weight of the new Sig replacement trigger?

[Wyoming Shooter]

My trigger scale indicates an average break of 4 lbs 15 oz. Range testing to follow. Best, ELN.

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https://www.youtube.com/watch?v=UgyArFYkl3Q
Wonder what they actually changed internally. The price has certainly gone up.

[Beat Trash]

I'd also be interested in seeing what has been changed. From what I can tell so far:

Heavier weight barrel.

The Sig two stage trigger that actually gives you a decent trigger pull comes installed.

Nicer M-Lok handguard.

"Cool Kids" colors, Grey or FDE

The stock is now 5 position vs. 3.

The overall weight went up about 1.5 lbs.

And of course, the price has been adjusted to match.

This would explain why Budsgunshop.com was able to buy up a bunch of MCX's and blow them out at $1,349.

I will be interested in seeing how the newer barrel shoots with a variety of bullet weights in 5.56mm

I have been kicking around buying an MCX Patrol from Buds all week. Yes it's cheaper than what I project the actual selling price of the Virtus will be. But I don't like the original MCX key mod hand guard and trigger. So I'd buy one of the new Midwest Industries M-Lok hand guards and one of the Sig triggers. All of the sudden the price difference is shrinking.

Side note, I just looked on the Sig Sauer web site. The picture of the original MCX patrol is still on the site, but when you try and click on the product to get information on the original MCX, it says, "page not found".

[Sensei]

Something tells me the Virtus is to the MCX what the Legion is to the P-Series. Basically, you're getting a much better trigger, heavier barrel, M-LOk rails, and some color options for about $300-500 more.

Perhaps the heavier barrel profile will address the accuracy issues that some 16" 5.56 rifles had after strings of fire.

As for full ambi, that is a bit of a stretch since the bolt release is still left sided only. Why they don't make a full ambi lower like the IWS or their own MPX is a bit mystifying.

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As for full ambi, that is a bit of a stretch since the bolt release is still left sided only.Charging handle is ambi, brah.

Reminds me of when Todd said that Sig tried to market the classic P-series as being ambi slide release, because you can slingshot it with either hand.

[MickAK]

I like the concept, and I like mine (Patrol, may get a .300 memeout barrel and suppressor depending on what legislation passes in the next few years)

The roll out was horrible. I've basically accepted having to fabricate my own handguards and other accessories. Not popular enough to have a good aftermarket. Doesn't look like it will be. I have no idea why they promised 7.62x39 capability when they had no intention of following up on it. The recall was weird. It's not an issue, I can't even get mine to do it dropping on a manually chambered round. Maybe it's just a blackout problem. I kept the original parts. I think the accuracy issues after strings of fire have to do with barrel swaps, out of spec torque, etc. It doesn't take much out of spec to cause an issue when you have heat expansion.

It's a fine, durable, reliable rifle that they tried to market as a lego kit, which was a mistake.

[HCM]

Geissele just announced an MCX specific trigger in the Facebook.

[Wyoming Shooter]

"The overall weight went up about 1.5 lbs. " I'd rather not. For me, the light weight of the original Patrol is a major plus. I've put more trouble-free rounds downrange the last few days. So far, so good.

[call_me_ski]

"The overall weight went up about 1.5 lbs. " I'd rather not. For me, the light weight of the original Patrol is a major plus. I've put more trouble-free rounds downrange the last few days. So far, so good.

Sig lists the weight difference as 1 pound. Not a terrible penalty considering the heavier barrel and the longer rail.

The Sig MCX is a platform that I really want to do well as I see potential in it. Sig has to step up and maintain QC and support the platform. I believe that they released the gun prematurely. The recall was evidence of this along with a charging handle that had a 250 round service life.

Despite the over the top marketing the Virtus is a step in the right direction. The new rail and receiver interface will allow for more versatility regarding the gas system and barrel lengths. The trigger should be nicer, and I am not a fan of pencil barrels. Along with the new charging handle that all MCX rifles are shipping with, the Virtus fixes the issues I had with the first MCX I had and subsequently sold.

I even like the grey color. I see personally see it as a homage to the original SIG 550 series of guns(yes, I know Sig Sauer has little to do with SIG or Swiss Arms). I hate to say it but Sig Sauer will likely get my money on this.

The 300blk pistol turned SBR is what will get my money. Now the question is do I jump on board now or do I wait for gen 4 in another six months? Even Sig Sauer is listing "The Final Chapter" as being 30 days away.

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http://soldiersystems.net/blog1/wp-content/uploads/2017/08/img_3625.jpg

http://soldiersystems.net/2017/08/22/sig-sauer-launches-mcx-rattler (http://soldiersystems.net/2017/08/22/sig-sauer-launches-mcx-rattler)

Interesting little micro variant. That 5.56 version is going to be ridiculous, though.

[Wyoming Shooter]

I ordered a Sig factory replacement trigger on 05/26/17. Total cost was $114. The trigger arrived 06/10/17. The packaging indicates "Made in United States" but does not designate the manufacturer. Replacing the MCX trigger is much like replacing a standard AR trigger. If you've not replaced an AR trigger before, I encourage you to watch some instructional videos or have a smith do the work. The new trigger is much smoother and lighter. My trigger scale indicates an average break of 4 lbs 15 oz. Range testing to follow. From the Big Empty, ELN.

FYI - The SIG factory replacement trigger was recalled ostensibly due to improper heat treat on some triggers. SIG notified me of the recall by email and included a pre-paid FedEx shipping label. The replacement for the replacement trigger arrived today - about 10 days turnaround. I will report back after it's been in use for awhile. Best, ELN.

[Wyoming Shooter]

Originally Posted by Wyoming Shooter View Post
I ordered a Sig factory replacement trigger on 05/26/17. Total cost was $114. The trigger arrived 06/10/17. The packaging indicates "Made in United States" but does not designate the manufacturer. Replacing the MCX trigger is much like replacing a standard AR trigger. If you've not replaced an AR trigger before, I encourage you to watch some instructional videos or have a smith do the work. The new trigger is much smoother and lighter. My trigger scale indicates an average break of 4 lbs 15 oz. Range testing to follow. From the Big Empty, ELN.


FYI - The SIG factory replacement trigger was recalled ostensibly due to improper heat treat on some triggers. SIG notified me of the recall by email and included a pre-paid FedEx shipping label. The replacement for the replacement trigger arrived today - about 10 days turnaround. I will report back after it's been in use for awhile. Best, ELN.

Some follow-up on the trigger saga: As earlier posted, the OEM trigger in my MCX was very heavy. At SIG's suggestion, I replaced the OEM trigger with the SIG "Match Grade AR Trigger Kit". This trigger was a great improvement over the OEM trigger. However, some were reportedly improperly heat treated and recalled. Here is a photo of the recalled trigger:

21449

At no expense to me, SIG replaced the recalled "Match Grade AR Trigger" with the SIG "Two-Stage Match Duo" shown here. The product package indicates "Made in United States" but does not state by whom. Installation was typical for ARs.

21450

Although I don't yet have any rounds down range with the "Match Duo" trigger, it feels very good. Average weight for the initial five presses was 4 lbs. 12.7 oz.

21451

I will report further after a few hundred rounds with the "Match Duo". Best, ELN.

[Spectre044]

I apologize in advance for the necro post. I found out recently that we are getting the virtus version of these in an 11.5 inch variety. I wanted to see if anyone had any follow up information on these rifles. They seem like a decent enough rifle but there is not a long track record with them and Sig doesn't have the best reputation for quality right now. Any further information from those of you who have been running them would be greatly appreciated.

[Tokarev]

Here are a couple more recent reviews:

https://www.americanrifleman.org/articles/2018/3/29/tested-sig-sauer-mcx-virtus-patrol-rifle/

https://www.shootingillustrated.com/articles/2018/3/26/review-sig-sauer-mcx-virtus-rifle/

[Spectre044]

Here are a couple more recent reviews:

https://www.americanrifleman.org/articles/2018/3/29/tested-sig-sauer-mcx-virtus-patrol-rifle/

https://www.shootingillustrated.com/articles/2018/3/26/review-sig-sauer-mcx-virtus-rifle/

Yeah, I have read both of those. Neither really tells me much. I was hoping someone here with hands on experience could chime in. Thanks though.

[Tokarev]

Yeah, I have read both of those. Neither really tells me much. I was hoping someone here with hands on experience could chime in. Thanks though.Well, I had some pretty good trigger time with one of the original Cabela's guns. It was a 16" gun and never used it as a 223. It ran well and had the auto-regulating gas system. Ran fine with supers and subs.

Later, once SIG announced they were switching to a manual gas system, I sent both barrels in for retrofit. After that the 300BLK seemed over-gassed when suppressed regardless of gas setting or ammo. I continually had issues with the gun stovepiping. Several trips back to SIG did not fix the problem. They eventually replaced the gun under warranty with a Virtus.

This new gun seems to run fine. I've used it with both the 300BLK and 223 barrels with and without my suppressor. Granted, I don't have a ton of rounds fired.

Overall, I like the gun. It is an interesting idea. Does it really offer much that can't be had from a DI AR or one of the piston guns out there. But it does have a QD barrel and a folding stock. If those are part of your requirement you should be happy.

Sent from my SM-G930P using Tapatalk

[Spectre044]

Well, I had some pretty good trigger time with one of the original Cabela's guns. It was a 16" gun and never used it as a 223. It ran well and had the auto-regulating gas system. Ran fine with supers and subs.

Later, once SIG announced they were switching to a manual gas system, I sent both barrels in for retrofit. After that the 300BLK seemed over-gassed when suppressed regardless of gas setting or ammo. I continually had issues with the gun stovepiping. Several trips back to SIG did not fix the problem. They eventually replaced the gun under warranty with a Virtus.

This new gun seems to run fine. I've used it with both the 300BLK and 223 barrels with and without my suppressor. Granted, I don't have a ton of rounds fired.

Overall, I like the gun. It is an interesting idea. Does it really offer much that can't be had from a DI AR or one of the piston guns out there. But it does have a QD barrel and a folding stock. If those are part of your requirement you should be happy.


That's the input I am looking for. Nothing the rifle offers is a requirement. I was just seeking information because these are what we are getting (we have no input) and I wanted to know what other's have experienced. Thanks.

[Tokarev]

That's the input I am looking for. Nothing the rifle offers is a requirement. I was just seeking information because these are what we are getting (we have no input) and I wanted to know what other's have experienced. Thanks.Well, if you're getting them issued as department guns you'll have more info than any of us soon.

Sent from my SM-G930P using Tapatalk

[Spectre044]

Well, if you're getting them issued as department guns you'll have more info than any of us soon.

Indeed. Once we receive them and start running them, I will chime back in. We should have them before the end of the calendar year. No specific timeframe though. Hopefully they run well.

[Tokarev]

Indeed. Once we receive them and start running them, I will chime back in. We should have them before the end of the calendar year. No specific timeframe though. Hopefully they run well.Conversion kits for legacy lowers or new complete guns?

Sent from my SM-G930P using Tapatalk

[Spectre044]

Conversion kits for legacy lowers or new complete guns?

Sent from my SM-G930P using Tapatalk

New complete guns.

[Sensei]

That's the input I am looking for. Nothing the rifle offers is a requirement. I was just seeking information because these are what we are getting (we have no input) and I wanted to know what other's have experienced. Thanks.

My 9” Gen2 in 300BLK has been reliable and accurate over about 500 rounds. Certainly not a torture test.

[Sensei]

I’m seriously considering a 5.5” Rattler upper for my NFA registered MCX lower. I’ve done some research and it appears that 120 grain supers are coming out of the barrel at 1800 fps. That means that Barnes 110 grain TAC-TXs should get at least 1800-1850. Keep in mind that these expand down to 1400 fps.

That means the Rattler with TAC-TX pills is about the size of a MP5K and significantly improved terminal performance against common intermediate barriers. This is a pretty cool option for a travel gun that reaches out to 150 yards with authority.

[HCM]

Indeed. Once we receive them and start running them, I will chime back in. We should have them before the end of the calendar year. No specific timeframe though. Hopefully they run well.

Did your Dept get the MCXs ? If so how have they worked out ?

[Spectre044]

Did your Dept get the MCXs ? If so how have they worked out ?

I don’t work there anymore but between two county agencies fielding several hundred, they performed well. No catastrophic failures and they proved to be reliable. I had a little over 7k through mine when I left and I only experienced 1 malfunction which I attribute to a worn magazine and not the rifle itself.

There are some drawbacks that I found. The biggest issue was with rail mounted IR lasers. The rail has what I find to be an unacceptable amount of flex. A shift of 2-3 inches at 25 yards is fairly easy to induce with relatively minimal pressure on the rail. This can be overcome some by mounting the laser more towards the receiver but it’s not ideal. They’re also heavier than a typical DI AR.

[HCM]

I don’t work there anymore but between two county agencies fielding several hundred, they performed well. No catastrophic failures and they proved to be reliable. I had a little over 7k through mine when I left and I only experienced 1 malfunction which I attribute to a worn magazine and not the rifle itself.

There are some drawbacks that I found. The biggest issue was with rail mounted IR lasers. The rail has what I find to be an unacceptable amount of flex. A shift of 2-3 inches at 25 yards is fairly easy to induce with relatively minimal pressure on the rail. This can be overcome some by mounting the laser more towards the receiver but it’s not ideal. They’re also heavier than a typical DI AR.

Thanks, I’ve heard about the rail being too light to hold zero with lasers. Apparently the rail supplied with the M 13 SURG kits is stiffer but of course sake doesn’t seem to sell it to the public.

Given the extra weight of a piston system I can understand Seguin wanting to make the lighter rail the default sense there are Few people actually running lasers, But it would be nice to have the option for those that do.

What length barrel were y’all running?

Did y’all have any accuracy issues ?

I understand some of the early MCX had a very light barrel profile and the longer barrels such as the 16 inch and 14.5 inch had some accuracy issues. Supposedly this was addressed with a slightly heavier barrel profile.

[Spectre044]

Thanks, I’ve heard about the rail being too light to hold zero with lasers. Apparently the rail supplied with the M 13 SURG kits is stiffer but of course sake doesn’t seem to sell it to the public.

Given the extra weight of a piston system I can understand Seguin wanting to make the lighter rail the default sense there are Few people actually running lasers, But it would be nice to have the option for those that do.

What length barrel were y’all running?

Did y’all have any accuracy issues ?

I understand some of the early MCX had a very light barrel profile and the longer barrels such as the 16 inch and 14.5 inch had some accuracy issues. Supposedly this was addressed with a slightly heavier barrel profile.

We were running 11.5 rifles. The majority of them were around 1-1.5 moa guns. If you want one for the the novelty of a piston gun, they performed well for us. I still prefer my DI rifles though. I don’t think you would go wrong with one.

[HCM]

We were running 11.5 rifles. The majority of them were around 1-1.5 moa guns. If you want one for the the novelty of a piston gun, they performed well for us. I still prefer my DI rifles though. I don’t think you would go wrong with one.

“The novelty of. Piston gun” in conjunction with my SIG LE dealer getting a few 16” 5.56 guns in at IOP pricing sparked my interest.

It’s a modular gun so theoretically if I like it I could do a form one and try to locate an 11.5” barrel.

[Spectre044]

“The novelty of. Piston gun” in conjunction with my SIG LE dealer getting a few 16” 5.56 guns in at IOP pricing sparked my interest.

It’s a modular gun so theoretically if I like it I could do a form one and try to locate an 11.5” barrel.

If you get a good deal on it, I vote go for it. I just bought one of the new ruger made marlin 1895 SBLs which I have less than zero use for but I like them and I’ve always wanted a 45-70. I’m all about buying what you want.

[HCM]

If you get a good deal on it, I vote go for it. I just bought one of the new ruger made marlin 1895 SBLs which I have less than zero use for but I like them and I’ve always wanted a 45-70. I’m all about buying what you want.

The price is right. Especially compared to a SCAR-16.

On another note.

I have a Marlin Guide Gun in 45-70 which I’ve had since the 1990s. You pretty much have to handload to make 45-70 affordable to shoot.

[Spectre044]

The price is right. Especially compared to a SCAR-16.

On another note.

I have a Marlin Guide Gun in 45-70 which I’ve had since the 1990s. You pretty much have to handload to make 45-70 affordable to shoot.

You’re not wrong. I’ve found a few boxes of fed hammer down for what I consider to be affordable 45-70. I ordered a few boxes of Buffalo bore which I’m sure will be brutal to shoot. And I have 2 boxes or hornady 325s which weren’t awful. I’m just glad I won’t be shooting it a lot because $50 for 20rds on the low end of the spectrum is rough.

[HeavyDuty]

“The novelty of. Piston gun” in conjunction with my SIG LE dealer getting a few 16” 5.56 guns in at IOP pricing sparked my interest.

It’s a modular gun so theoretically if I like it I could do a form one and try to locate an 11.5” barrel.

You’re thinking a rebarrel instead of a second upper? I’m watching for an 11.5” 5.56 upper to make my Rattler more versatile, and will probably form 1 it. It’s too expensive to travel with it as a pistol anyways, and I’m NY screwed (landlocked.) I think complete uppers may be easier to find.

[call_me_ski]

From my experience the MCX is the best thing going if you want a piston gun on an Ar15 lower.

[HCM]

You’re thinking a rebarrel instead of a second upper? I’m watching for an 11.5” 5.56 upper to make my Rattler more versatile, and will probably form 1 it. It’s too expensive to travel with it as a pistol anyways, and I’m NY screwed (landlocked.) I think complete uppers may be easier to find.

I'll take what I can find.

[HeavyDuty]

Posting to both the MCX and Rattler threads - there was question at the SIG Academy Pro Shop about what works with what, they suggested I contact customer support. I just heard back:


Thank you for contacting Sig Sauer

For Clarity: The upper receiver from all MCX models, including the Rattler, are compatible with all other MCX lower receivers. (Including a Rattler lower). The barrels from the Virtus can be used on older, Legacy MCX rifles, as they include the tapered lug bolt that will need to be used. The Rattler upper will work with a standard MCX lower, but cannot accept other MCX length barrels as the upper is unique in design in regards to recoil and gas management. Rattler barrels cannot be used with other MCX models either.

Kindest,

So, with that I’ll start keeping an eye out for a complete 11.5” 5.56 upper assembly.

[JCN]

I just ordered MCX Virtus in 16” and 11.5” for 5.56.

[HeavyDuty]

I just ordered MCX Virtus in 16” and 11.5” for 5.56.

Supposedly the 11.5” is back in production. I’ve had a complete 11.5” upper on order for about a month now, hopefully it will show up before I’m too old to enjoy it. And I’m waiting for my Rattler Form 1 to finish processing.

[JCN]

87432

[HeavyDuty]

87432

That was fast! I was on the phone with SIG CS today on an unrelated issue, and the rep said that he thought my upper would be in stock sooner rather than later.

[JCN]

That was fast! I was on the phone with SIG CS today on an unrelated issue, and the rep said that he thought my upper would be in stock sooner rather than later.

87435

“I love you, you love me, we’re a happy family!”

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As an aside, apparently the Virtus and Rattlers can have pretty bad deflection/shift of the handguard, thus making it a crapshoot as to its viability for use with an MFAL:


Its been pretty hashed over here and other places. It really comes down to the individual rail/gun. Some have voiced concern/issues, others say there are no issues with theirs.

Ultimately, the MCX/LVAW hand guard is attached to the weapon system using high-tolerance rails and your forward takedown/pivot pin. It doesn't use an attachment that interacts with a barrel nut (there isn't a barrel nut), it doesnt interact with the upper/lower receivers. It's primary mission is to have sturdy-enough real estate for your offhand to interact with.

The fix is easy - mount your laser to the upper receiver. It's even referenced in this video you linked, where he adds that the "unit" operators he saw had their lasers mounted to the rear. Great idea. Individual testing of your rifle/handguard will tell you whether or not you can mount to your rail and those results can help you make the decision on how to config your rifle based on your tolerance to those results.

I have a couple of rails - both commercially available and as-issued LVAW - that have ZERO issue with POA/POI shift. I have ran over them, dropped them, banged them, you name it. Will they all be like that? No, its not realistic to expect this system to do that. Including the LVAW - the LVAW is really no different, in this regard. It has some changes to it vs the commercially available version.

Some of you have seen the "Gen3" MCX upper that's been floated around several different media mediums. You can probably draw your own conclusions about where those visible changes are being referenced from and therefore how they are/will be implemented.

ETA: This is not an identified "issue" that is driving platform change. Just clarifying based on my statements below.Source: https://www.ar15.com/forums/Armory/MCX-Rail-Deflection/45-531647/#i5614629

This kills a lot of my interest in the platform, though it's been pretty low ever since I slapped a LAW onto my 10.3" build.

[JCN]

As an aside, apparently the Virtus and Rattlers can have pretty bad deflection/shift of the handguard, thus making it a crapshoot as to its viability for use with an MFAL:

Source: https://www.ar15.com/forums/Armory/MCX-Rail-Deflection/45-531647/#i5614629

This kills a lot of my interest in the platform, though it's been pretty low ever since I slapped a LAW onto my 10.3" build.

One of the things I do on my MPXs is I use adhesive foam in the mating between the handguard and the upper to add tension and remove wiggles.

[Default.mp3]

One of the things I do on my MPXs is I use adhesive foam in the mating between the handguard and the upper to add tension and remove wiggles.I am curious as to how that affects POA/POI shifts and deflection; the foam might take out obvious rattling and perhaps help with light pressure (I believe one of the P&S modcasts had a speaker say that even resting their handguard on something, no loading, caused very noticeable shifts), but I would assume that its compressibility would mean that overall POI/POA shifts and deflection would still occur when loading the handguard (bipod, barricade bracing, etc.).

Obviously, there are other options to get around this whole issue, but would depend on the MFAL in use as to its viability (e.g., a MAWL on a GBRS mount would kill a lot of the advantages of the MAWL).

[JCN]

I am curious as to how that affects POA/POI shifts and deflection; the foam might take out obvious rattling and perhaps help with light pressure (I believe one of the P&S modcasts had a speaker say that even resting their handguard on something, no loading, caused very noticeable shifts), but I would assume that its compressibility would mean that overall POI/POA shifts and deflection would still occur when loading the handguard (bipod, barricade bracing, etc.).

Obviously, there are other options to get around this whole issue, but would depend on the MFAL in use as to its viability (e.g., a MAWL on a GBRS mount would kill a lot of the advantages of the MAWL).

I don’t have a laser handy, but the upper rail on the Virtus extends pretty far forward before turning into hand guard so maybe it could be worked around.

[JCN]

87457

[Default.mp3]

Oh hey, MCX Gen3:
https://youtu.be/-cSBjUKVJUU?t=43

Not much detail, BLUF:

1 lb lighter (didn't say which configuration)
Compatible with standard AR triggers
7.62×39mm option

[Ndbbm]

I’d like at least the new hand guard, if it will fit, for my rattler. A lighter upper would be nice too.

Jason

[JCN]

I just submitted for 11.5” SBR paperwork on the Virtus.

[JCN]

Added a magwell and a radian charging handle.

87656

[DMCutter]

I managed about an MOA group out of my MCX Virtus 9" 300 blackout last Friday afternoon with 110 grn Vmax at 200 yards with a Juliet 3 and Romeo 4t once I figured out which ranging dot to use. I'm thoroughly impressed with it and now I'm wondering if I need a 5.56 patrol to go with it. Maybe gen 2 prices will come down when they release gen 3.

[JCN]

I ordered MCX specific gaming Hiperfire triggers to be closer to my MPX triggers.

I think I’m going to go more gamer on these guns because that’s my main use and enjoyment for firearms.

So maybe something I could use in a 2-gun setting.

I’ve never shot anything with a magnified optic or longer than 100 yards as a long gun noob but this might be the gateway drug…

[littlejerry]

I ordered MCX specific gaming Hiperfire triggers to be closer to my MPX triggers.

I think I’m going to go more gamer on these guns because that’s my main use and enjoyment for firearms.

So maybe something I could use in a 2-gun setting.

I’ve never shot anything with a magnified optic or longer than 100 yards as a long gun noob but this might be the gateway drug…

How's your overall fitness? You might try a biathlon or run'n'gun event. They made USPSA boring for me.

[DMCutter]

I ordered MCX specific gaming Hiperfire triggers to be closer to my MPX triggers.

I think I’m going to go more gamer on these guns because that’s my main use and enjoyment for firearms.

So maybe something I could use in a 2-gun setting.

I’ve never shot anything with a magnified optic or longer than 100 yards as a long gun noob but this might be the gateway drug…

I have a Hiperfire Eclipse in my MPX and it's awesome, but I tend to think of my MCX as my most versatile SHTF gun and I think a 3lb single stage trigger might not be ideal. But it sure is tempting.

[JCN]

I have a Hiperfire Eclipse in my MPX and it's awesome, but I tend to think of my MCX as my most versatile SHTF gun and I think a 3lb single stage trigger might not be ideal. But it sure is tempting.

I was talking with Mike C on this one with me trying to figure out what real world application I could have for my MCXs…

Eventually I had to admit to myself that I enjoy gaming and that’s going to be 99.99% of my use for firearms.

I’ll leave a heavy X95 in the bedroom gun safe and game the fun guns and enjoy them.

And hey, if true zombie apocalypse… maybe I do want a 2 pound gamer trigger? :D

[JCN]

87707

This arrived today….

[RAM Engineer]

This arrived today….

Is that an MCX Virtus Patrol? Gray?

[HeavyDuty]

The 11.5” 5.56 uppers are back on the SIG website - they were gone for a long time. Hopefully that means production is in process. I was able to get mine ordered last month with my class discount for a pretty substantial savings.

https://www.sigsauer.com/mcx-virtus-upper-assembly-11-5-inch-5-56-nato.html

Now if BATFE would just get my Form 1 approved…

[zpelletier]

The 11.5” 5.56 uppers are back on the SIG website - they were gone for a long time. Hopefully that means production is in process. I was able to get mine ordered last month with my class discount for a pretty substantial savings.

https://www.sigsauer.com/mcx-virtus-upper-assembly-11-5-inch-5-56-nato.html

Now if BATFE would just get my Form 1 approved…

Out of stock. I wonder how long before they’re back again

[HeavyDuty]

Out of stock. I wonder how long before they’re back again

Just to clarify - they haven’t been in stock, just shown as coming soon. But this is an improvement over just a few weeks ago where they weren’t on the website at all.

[zpelletier]

Just to clarify - they haven’t been in stock, just shown as coming soon. But this is an improvement over just a few weeks ago where they weren’t on the website at all.

Ah I see.

It’ll be interesting to see if they ramp up production or not. It seems like for years everything MCX has been hard to come by and I’m sure that demand will only increase with the NGSW contract

[JCN]

Mounted a 7.5 MOA triangle offset.

87763

Waiting for a Scalarworks/Nightforce combo to come back to stock.

Also…

87764

[DMCutter]

Can anyone comment on the accuracy the MCX Virtus patrol with green tip? Most of my stash is XTac and Norma SS109 and my 516 and x95 do pretty well with it.

[JCN]

Got my 11.5” Virtus SBR approved in 10 days efile.

Submitting my Canebrake rattler tonight as well.

[Corse]

Got my 11.5” Virtus SBR approved in 10 days efile.

Submitting my Canebrake rattler tonight as well.

How did you do the electronic fingerprints?

[JCN]

How did you do the electronic fingerprints?

I have fingerprints on file at silencershop and they can turn them into paper cards they mail you.

But I also went in person and got a stack of fingerprints done at the local Sheriff and mail those out the day after I efile the form.

[JCN]

88230

If I’m going to shoot long guns I should do long gun type things!

[RAM Engineer]

Did SIG ever release commercial versions of the LVAW or SURG? Seems like a missed opportunity for a company that released LRIP examples of their M5 before they were even awarded a contract.

[hlb14]

I'm not sure if the Ratler Canebreak was their commercial version of the SURG but Lipsys distributed a model of MCX called the Tacops that looks like a version of the LVAW.

[RAM Engineer]

I'm not sure if the Ratler Canebreak was their commercial version of the SURG but Lipsys distributed a model of MCX called the Tacops that looks like a version of the LVAW.

Thanks for the info on the Tacops. I was unaware about that. That does appear to be a LVAW clone. I also think the Canebreak is actually more similar to the LVAW than it is the SURG, but with different barrel length and handguard lengths. I'm not sure why SIG didn't settle on the 6.75" barrel length for the Canebreak instead of the Rattler 5.5" length.

From a ballistic POV, what does a subsonic 300 Whisper from a 5.5" barrel do, compared to a 147 gr 9mm from the same barrel length?

SURG was a 5.56 upper with at least a 11.5" barrel.
https://soldiersystems.net/2018/08/02/first-look-socoms-new-suppressed-upper-receiver-group-from-sig-sauer/

[JCN]

From a ballistic POV, what does a subsonic 300 Whisper from a 5.5" barrel do, compared to a 147 gr 9mm from the same barrel length?

Subsonic 147gr is around 1050 fps or so.

Subsonic 300 blackout to stay around 1050 will be a 200-220gr bullet.

Theoretically better barrier penetration.

But it’s really going to depend on what ammo you use.

There aren’t great subsonic 300 blackout rounds that reliably expand out of short barrels that I’ve seen. The underwood grappling hook above has been the most reliable for me.

EDIT: I just googled this from Sig that was designed for special forces use.

https://www.firearmsnews.com/editorial/sig-sauer-expanding-300-blk-vcrown-how-good-is-it/378618

[RAM Engineer]

EDIT: I just googled this from Sig that was designed for special forces use.

https://www.firearmsnews.com/editorial/sig-sauer-expanding-300-blk-vcrown-how-good-is-it/378618

This looks like a similar design, but a different nosecone:

https://www.midwayusa.com/product/1023728449?pid=659610

[JCN]

This looks like a similar design, but a different nosecone:

https://www.midwayusa.com/product/1023728449?pid=659610

Nice! Good find, thanks for sharing!

[JCN]

This looks like a similar design, but a different nosecone:

https://www.midwayusa.com/product/1023728449?pid=659610

FWIW, my MCX 300 blk has a 1:6 barrel and I didn’t have suppressor baffle strikes with that.

[RAM Engineer]

Here's where I'm at:


I'm a lefty.
I have a Mk18 (10.5" 5.56) clone by SAW, that is gassed on the "reliable" side of things. With my AAC M4-2000 can on it, it is unbearable to shoot suppressed (gas to the face from the ejection port).
I just bought an HK SP5 that I plan on suppressing, because MP5=awesome for those of us who grew up in the 80s.
I keep wondering if a short (5.5"-6.75") .300 gun (MCX) is the best of both worlds, or the worst of both worlds for a small suppressed gun.
...OR do I try to find a SURG type 5.56 upper that is gassed to run full time suppressed and see how that works out for me instead.

[jh9]

Here's where I'm at:


I'm a lefty.
I have a Mk18 (10.5" 5.56) clone by SAW, that is gassed on the "reliable" side of things. With my AAC M4-2000 can on it, it is unbearable to shoot suppressed (gas to the face from the ejection port).


Thread drift but... as another lefty, getting what amounts to a double dose (or more) of gas to the face from a semi-auto is the reason I'm looking at Surefire cans. AFAIK they're about as far as you can go down the "lowest backpressure / least gassy" rabbit hole. No first hand experience there, though. On the fence if it's worth a thousand bucks + some months to find out.

[JCN]

Here's where I'm at:


I'm a lefty.
I have a Mk18 (10.5" 5.56) clone by SAW, that is gassed on the "reliable" side of things. With my AAC M4-2000 can on it, it is unbearable to shoot suppressed (gas to the face from the ejection port).
I just bought an HK SP5 that I plan on suppressing, because MP5=awesome for those of us who grew up in the 80s.
I keep wondering if a short (5.5"-6.75") .300 gun (MCX) is the best of both worlds, or the worst of both worlds for a small suppressed gun.
...OR do I try to find a SURG type 5.56 upper that is gassed to run full time suppressed and see how that works out for me instead.


I have a 16” Tavor X95 with 300 blk that suppresses great and shorty length.

[RAM Engineer]

I have a 16” Tavor X95 with 300 blk that suppresses great and shorty length.

That's a good idea I hadn't considered. I planned to set up an AUG for .556 suppressed (set up for left-hand ejection) and the X95 might be a good compliment in 300.

[JCN]

That's a good idea I hadn't considered. I planned to set up an AUG for .556 suppressed (set up for left-hand ejection) and the X95 might be a good compliment in 300.

I did the Midwest industries sealing plate and I don’t find it gassy at all. I don’t remember if I added a little bit of silicone caulk to that as well (on the inside).

X95 at least has ambi mag release and can be left sided set up.

There are some aftermarket triggers that make it decent and it’s a good compromise for suppression in getting a long barrel in a short package.

[RAM Engineer]

I did the Midwest industries sealing plate

Manticore?

[JCN]

Manticore?

Midwest. Here’s a link.

https://www.midwestindustriesinc.com/MI-Tavor-Ejection-Port-Cover-p/mi-tpdc-blk.htm

88400

I have a Manticore on a different Tavor and they both work fine. I think the last time I just got what was in stock.

88401

[DMCutter]

I have a Super Sabra trigger pack and Lightning Bow in my X95 and it's the best trigger I have in any gun except maybe the Hiperfire in my MPX. I converted mine back to 5.56 from 300 after I got my 9" MCX Virtus 300 pistol because I figured the 9" barrel got me about the best performance I could reasonably expect out of the caliber; the X95 isn't exactly renowned for its accuracy so I didn't think the 16" barrel would get me much more usable range.

[JCN]

Working on a couple things that are silly but mainly for entertainment.

Have a 16” 300 blk MCX barrel that I am having cut down to 9”.

The gas block is in a different place than the 6-9” factory barrels and the Rattler barrel.

Compared to the 6-9” the piston has a longer plunger and compared to the Rattler the point of the op rod is longer.

So it might not make as much gas. But that might actually be a good thing…

Going to try and get it to work on my Rattler.

Will put it together when parts come in.

[DMCutter]

Not sure if this is the right thread, but it's kind of apropos. I don't know the source of the photo but that rifle sure looks like an MCX of some sort.
88484

[HeavyDuty]

Working on a couple things that are silly but mainly for entertainment.

Have a 16” 300 blk MCX barrel that I am having cut down to 9”.

The gas block is in a different place than the 6-9” factory barrels and the Rattler barrel.

Compared to the 6-9” the piston has a longer plunger and compared to the Rattler the point of the op rod is longer.

So it might not make as much gas. But that might actually be a good thing…

Going to try and get it to work on my Rattler.

Will put it together when parts come in.

You are like a mad scientist.

88490

[DMCutter]

I've had 2 range sessions where I had my Romeo 4T on my MCX 300 zeroed and my first string of fire was about 4" low and left at 100 yards. The mount was tight so I rezeroed and continued to march. I thought maybe the sight was f'ed up but I didn't really want to send it back to Sig. I finally got a Wheeler FAT wrench and just checked the barrel bolts and neither was close to 60 in-lb. Hopefully that was the reason for the shift. When it stops raining I'll go to the range and see what it looks like.

[HeavyDuty]

I've had 2 range sessions where I had my Romeo 4T on my MCX 300 zeroed and my first string of fire was about 4" low and left at 100 yards. The mount was tight so I rezeroed and continued to march. I thought maybe the sight was f'ed up but I didn't really want to send it back to Sig. I finally got a Wheeler FAT wrench and just checked the barrel bolts and neither was close to 60 in-lb. Hopefully that was the reason for the shift. When it stops raining I'll go to the range and see what it looks like.

I’ll check my Rattler - thanks for the heads-up!

[DMCutter]

Tightening the bolts made a couple clicks difference. I got it zeroed again with 150 grain Ammo Inc FMJ and all was good. I finished up with a couple mags of 108 grain frangible and 125 grain PPU hp and POI was about 3" high. Muzzle velocity of the 150 is about 1850 fps and the lighter loads are close to 2200, so I guess that makes sense. Still minute of badguy, I just need to be conscious of what I've got in my mags.

[JCN]

Something interesting that I’ve noticed for 300 blackout twist rates:

Rattler: 1:5
Tacops 6.75: 1:5
9”: 1:5
16”: 1:6

Wonder how a cut down 16 will work…

[JCN]

I wonder if the low twist rate was to destabilize the bullets for subsonic close work (a la the article).

Might contextualize the range ability of the 300 MCX.

I don’t normally do long range stuff but might be worth comparing the 100 yard group of the 1:5 rattler with a 1:6 cut down 16

[JRB]

Here's where I'm at:


I'm a lefty.
I have a Mk18 (10.5" 5.56) clone by SAW, that is gassed on the "reliable" side of things. With my AAC M4-2000 can on it, it is unbearable to shoot suppressed (gas to the face from the ejection port).
I just bought an HK SP5 that I plan on suppressing, because MP5=awesome for those of us who grew up in the 80s.
I keep wondering if a short (5.5"-6.75") .300 gun (MCX) is the best of both worlds, or the worst of both worlds for a small suppressed gun.
...OR do I try to find a SURG type 5.56 upper that is gassed to run full time suppressed and see how that works out for me instead.



Thread drift but... as another lefty, getting what amounts to a double dose (or more) of gas to the face from a semi-auto is the reason I'm looking at Surefire cans. AFAIK they're about as far as you can go down the "lowest backpressure / least gassy" rabbit hole. No first hand experience there, though. On the fence if it's worth a thousand bucks + some months to find out.

/thread drift and all, but I'd humbly suggest an EZtune gas tube from Black River Tactical that can effectively reduce your gas port size with very minimal fuss:
https://blackrivertactical.com/WP/BRT-EZTUNE-Gas-Tube-Configurable-Carbine-p103167251

After seeing it recommended by Casual Friday I opted for a couple for my own 6933 uppered pistols/soon-to-be SBR's, and I couldn't be happier as a cross-dominant weirdo that's left eyed and right handed.

[Casual Friday]

/thread drift and all, but I'd humbly suggest an EZtune gas tube from Black River Tactical that can effectively reduce your gas port size with very minimal fuss:
https://blackrivertactical.com/WP/BRT-EZTUNE-Gas-Tube-Configurable-Carbine-p103167251

After seeing it recommended by Casual Friday I opted for a couple for my own 6933 uppered pistols/soon-to-be SBR's, and I couldn't be happier as a cross-dominant weirdo that's left eyed and right handed.

I was sold after running 5 rounds through it. It's like you're not even shooting suppressed. The BRT tubes have spoiled me.

[JCN]

So just FYI, this is the top rail gap issue that happens when you try and put a Virtus hand guard on a Rattler.

88625

And this is the Virtus op rod that I can use with the rattler bolt to use a Virtus barrel.

88626

I’m expecting less gas for the cut down frankenbarrel…

I’m going to use what I know from my MPX experimentation.

It might work out really well to try MPX springs in the MCX to soften recoil with reduced gas and add back reliability margin with less gas.

Might make shooting the rattler suppressed more pleasant too!

[HCM]

I wonder if the low twist rate was to destabilize the bullets for subsonic close work (a la the article).

Might contextualize the range ability of the 300 MCX.

I don’t normally do long range stuff but might be worth comparing the 100 yard group of the 1:5 rattler with a 1:6 cut down 16

Unnecessary.

Remember for serious application for 300 blackout is to be a better sub machine gun than 9mm versions.

[JCN]

Unnecessary.

Remember for serious application for 300 blackout is to be a better sub machine gun than 9mm versions.

It’s mainly my curiosity of trying to reverse engineer Sig being Sig.

Sometimes they do things for bizarre reasons.

Why make a 16” 300 blk barrel at all? For non-SBR compliance? For people who want to hunt hogs?

I don’t know.

I also don’t know why they chose 1:6 for their carbine and more importantly if that hurts my application of it cut down compared to a purpose built and bought 9” 1:5…

I also don’t know why they sold a 5.5” rattler when it was initially designed as a 6.75 from what I read?

So I don’t know when Sig is doing things for good reasons versus pandering to the almighty buck.

[HCM]

It’s mainly my curiosity of trying to reverse engineer Sig being Sig.

Sometimes they do things for bizarre reasons.

Why make a 16” 300 blk barrel at all? For non-SBR compliance? For people who want to hunt hogs?

I don’t know.

I also don’t know why they chose 1:6 for their carbine and more importantly if that hurts my application of it cut down compared to a purpose built and bought 9” 1:5…

I also don’t know why they sold a 5.5” rattler when it was initially designed as a 6.75 from what I read?

So I don’t know when Sig is doing things for good reasons versus pandering to the almighty buck.

Many states do not allow NFA and many require minimum calibers for hunting deer and hogs etc.

The rattler was designed for a customer who had a requirement for a minimally sized bag gun in a rifle caliber / shooting supers.

If running a bad gun in a true non permissive environment every little bit counts.

[JCN]

The rattler was designed for a customer who had a requirement for a minimally sized bag gun in a rifle caliber / shooting supers.

If running a bad gun in a true non permissive environment every little bit counts.

Can you confirm that the gun was originally designed with the 6.75” barrel instead of the 5.5”?

I’m just trying to figure out if the original design was different than the commercial rattler and then figure out what parts are function and what parts are fantasy?

Is it like the 6” shorty ARs?
Or 2” 357 magnums?

There comes a point where there is minimal barrel length to accomplish what you’re trying to accomplish.

For me, a rifle shooting supers should get through IIIA and I can’t do it with the TTSX from a 5.5 rattler.

[HCM]

Can you confirm that the gun was originally designed with the 6.75” barrel instead of the 5.5”?

I’m just trying to figure out if the original design was different than the commercial rattler and then figure out what parts are function and what parts are fantasy?

Is it like the 6” shorty ARs?
Or 2” 357 magnums?

There comes a point where there is minimal barrel length to accomplish what you’re trying to accomplish.

For me, a rifle shooting supers should get through IIIA and I can’t do it with the TTSX from a 5.5 rattler.

I can’t confirm the barrel length but I can confirm the purpose/requirement it was created for. It was created for people who needed a small gun that fit in a bag for non-permissive environments and shooting .300 supers.

Remember, the metric is “better than a 9mm SMG” - if the people that were made for need to get through soft armor they could get AP ammo. Supers with TSX /all copper bullets hit harder and have a greater effective range than a 9mm from something like an MPX-K.

There is 9 mm armor piercing ammo that will go through IIIA from a typical SMG barrel, so no reason to think .300 super AP ammo couldn’t do it as well.

But there is no free lunch, AP ammo would go through soft armor but it will also over penetrate and reduce terminal ballistic effects.

Again non-permissive environments where it’s a loaded rattler ready to go, a MK 18 unloaded and broken into two parts or no rifle at all.

[JCN]

HCM

Thinking about it more, you are right and I think I’m thinking about the Rattler wrong.

For home defense I’m probably better served with a short Virtus than a long Rattler.

[HCM]

HCM

Thinking about it more, you are right and I think I’m thinking about the Rattler wrong.

For home defense I’m probably better served with a short Virtus than a long Rattler.

For HD, I’s want either an 11.5” or a 9” with a suppressor.

[Clusterfrack]

For HD, I’s want either an 11.5” or a 9” with a suppressor.

Agree. For HD I use a 5.56 SBR. I like that 5.56 bullets tend to stop when they hit walls.

[JCN]

For HD, I’s want either an 11.5” or a 9” with a suppressor.


Agree. For HD I use a 5.56 SBR. I like that 5.56 bullets tend to stop when they hit walls.

My current HD is a suppressed 16” bullpup 5.56 with Gold Dot. It has good balance in that configuration.

Been looking to see if I can / should go to something more MPX-ish since I’m spending so much time with that platform.

But I’m coming to the conclusion that like pistol, if I get good enough with fundamentals it won’t really matter which weapon platform / system I run for HD.

[JCN]

https://sigsauerparts.com/sig-sauer-mcx-upper-receiver-assembly-gen-2-black/

Upper for sale $399 in black.

Going to use that with the 9” blackout on the rattler lower.

Going to rattle can the Virtus handguard that came with the blackout barrel.

Basically just need to swap bolt carrier group over with the new op rod.

[JCN]

Since I have a Canebrake rattler, going to experiment with different length handguards to make things as small as possible.

Optics planet has a short rattler handguard for $140…

[HeavyDuty]

I've had 2 range sessions where I had my Romeo 4T on my MCX 300 zeroed and my first string of fire was about 4" low and left at 100 yards. The mount was tight so I rezeroed and continued to march. I thought maybe the sight was f'ed up but I didn't really want to send it back to Sig. I finally got a Wheeler FAT wrench and just checked the barrel bolts and neither was close to 60 in-lb. Hopefully that was the reason for the shift. When it stops raining I'll go to the range and see what it looks like.


I’ll check my Rattler - thanks for the heads-up!


Tightening the bolts made a couple clicks difference. I got it zeroed again with 150 grain Ammo Inc FMJ and all was good. I finished up with a couple mags of 108 grain frangible and 125 grain PPU hp and POI was about 3" high. Muzzle velocity of the 150 is about 1850 fps and the lighter loads are close to 2200, so I guess that makes sense. Still minute of badguy, I just need to be conscious of what I've got in my mags.

I’m glad I checked. Both were well short of even 40 in-lb.

[DMCutter]

Damn. Sig is gonna get us kilt in da streets. Interested to know what effect on your zero tightening them will have.

[JCN]

Virtus upper arrived so I can put it on the rattler lower.

88869

[JCN]

The shooter in the Buffalo killings was wearing body armor.

“The gunman shot four people outside the store, three fatally, said Buffalo Police Commissioner Joseph Gramaglia. Inside the store, security guard Aaron Salter, a retired Buffalo police officer, fired multiple shots. A bullet hit the gunman's bulletproof armor but had no effect, Gramaglia said.

The gunman then killed the guard, the commissioner said, then stalked through the store shooting other victims.”

If I’m going to have a long-ish gun, I want it to be able to do long gun things.

[JCN]

I’m channeling my inner HCM

If I’m going to go small, go small.

MI handguard and Vulcan ACSS optic.

Muzzle brake threaded for Rugged Razor.

89046

[Corse]

The shooter in the Buffalo killings was wearing body armor.

“The gunman shot four people outside the store, three fatally, said Buffalo Police Commissioner Joseph Gramaglia. Inside the store, security guard Aaron Salter, a retired Buffalo police officer, fired multiple shots. A bullet hit the gunman's bulletproof armor but had no effect, Gramaglia said.

The gunman then killed the guard, the commissioner said, then stalked through the store shooting other victims.”

If I’m going to have a long-ish gun, I want it to be able to do long gun things.

If it’s plates no luck anyway. If it’s soft armor, supersonic 300 blk should punch through it no problem. The biggest issue would be actually having the MCX available in the first place. You’d probably be working with a 9mm most likely.

[JCN]

If it’s plates no luck anyway. If it’s soft armor, supersonic 300 blk should punch through it no problem.

False.

89052

Supersonic Barnes TTSX does NOT penetrate IIIA.

The Rattler barrel is just too short and too slow with standard conventional 300 supers.

In the supermarket shooting, there wouldn’t have been time to deploy an MCX.

But if you did have a Rattler with supers, you might be sorely disappointed when encountering IIIA.

89053

[Corse]

False.

89052

Supersonic Barnes TTSX does NOT penetrate IIIA.

The Rattler barrel is just too short and too slow with standard conventional 300 supers.

In the supermarket shooting, there wouldn’t have been time to deploy an MCX.

But if you did have a Rattler with supers, you might be sorely disappointed when encountering IIIA.

89053

Interesting. Is this the 110 or 120 gr? Do you know the velocity?

I’ve chronographed the 110s at over 2000 FPS from the rattler. They were definitely on the hot side though.

[Wondering Beard]

False.

89052

Supersonic Barnes TTSX does NOT penetrate IIIA.

The Rattler barrel is just too short and too slow with standard conventional 300 supers.

In the supermarket shooting, there wouldn’t have been time to deploy an MCX.

But if you did have a Rattler with supers, you might be sorely disappointed when encountering IIIA.

89053

That load has, as I understand it, a polymer tip which, at least theoretically, would bend when encountering armor thus limiting its capability to penetrate.

I hope someone who knows those loads well would confirm, and I wonder if other loads, without such a tip, would actually penetrate.

[WobblyPossum]

False.

89052

Supersonic Barnes TTSX does NOT penetrate IIIA.

The Rattler barrel is just too short and too slow with standard conventional 300 supers.

In the supermarket shooting, there wouldn’t have been time to deploy an MCX.

But if you did have a Rattler with supers, you might be sorely disappointed when encountering IIIA.

89053

That’s really interesting. I’d love to see more testing. My understanding is that the TTSX is the go-to supersonic bullet for short-barreled .300 blk. It’s surprising to see it can’t reliably penetrate soft armor. I wonder if this is the case for all supersonic .300 blk that isn’t specifically marketed as armor piercing, when fired from such a short barrel, or if this is specific to the TTSX. I’d be curious how some of the newer solid-copper stuff would do. If supersonic .300 blk out of a short barrel does generally have a tough time with soft armor, what are the advantages of supersonic over subsonic ammunition in something like a Rattler?

[JCN]

That’s really interesting. I’d love to see more testing. My understanding is that the TTSX is the go-to supersonic bullet for short-barreled .300 blk. It’s surprising to see it can’t reliably penetrate soft armor. I wonder if this is the case for all supersonic .300 blk that isn’t specifically marketed as armor piercing, when fired from such a short barrel, or if this is specific to the TTSX. I’d be curious how some of the newer solid-copper stuff would do. If supersonic .300 blk out of a short barrel does generally have a tough time with soft armor, what are the advantages of supersonic over subsonic ammunition in something like a Rattler?

I do a lot of armor testing but I don’t usually post it online for reasons.

[WobblyPossum]

I do a lot of armor testing but I don’t usually post it online for reasons.

Totally understandable.

[Sensei]

Interesting. Is this the 110 or 120 gr? Do you know the velocity?

I’ve chronographed the 110s at over 2000 FPS from the rattler. They were definitely on the hot side though.

Your results a good bit off what I’ve experienced and seen with the 110 grain Barnes load. Take a look at post 1 and 10 here:

https://pistol-forum.com/showthread.php?26978-Factory-Ammo-Chrono-Results-from-Various-Barrel-Lengths

The Rattler gave up 300 fps to a 9” MCX and came in at around 1825 fps. While this is enough velocity to expand in soft tissue within 25 yards and after many barriers, I’m not surprised that it chokes on soft armor. FWIW, I’ve seen other articles on the load that quote around 1800 fps for the 110 grain Barnes load out of a Rattler and 2100 fps from 9” barrels; none as high as 2K from the Rattler.

[JCN]

Your results a good bit off what I’ve experienced and seen with the 110 grain Barnes load. Take a look at post 1 and 10 here:

https://pistol-forum.com/showthread.php?26978-Factory-Ammo-Chrono-Results-from-Various-Barrel-Lengths

The Rattler gave up 300 fps to a 9” MCX and came in at around 1825 fps. While this is enough velocity to expand in soft tissue within 25 yards and after many barriers, I’m not surprised that it chokes on soft armor. FWIW, I’ve seen other articles on the load that quote around 1800 fps for the 110 grain Barnes load out of a Rattler and 2100 fps from 9” barrels; none as high as 2K from the Rattler.

1800 versus 2100 were almost exactly what I got as well.

[Corse]

Your results a good bit off what I’ve experienced and seen with the 110 grain Barnes load. Take a look at post 1 and 10 here:

https://pistol-forum.com/showthread.php?26978-Factory-Ammo-Chrono-Results-from-Various-Barrel-Lengths

The Rattler gave up 300 fps to a 9” MCX and came in at around 1825 fps. While this is enough velocity to expand in soft tissue within 25 yards and after many barriers, I’m not surprised that it chokes on soft armor. FWIW, I’ve seen other articles on the load that quote around 1800 fps for the 110 grain Barnes load out of a Rattler and 2100 fps from 9” barrels; none as high as 2K from the Rattler.

My results are for hand loads at or near max with a magnetoSpeed, so I imagine they are correct.

I think my results for factory loads are about what you stated.

[JCN]

My results are for hand loads at or near max with a magnetoSpeed, so I imagine they are correct.

I think my results for factory loads are about what you stated.

I wish Underwood would load them hot like that.

[JCN]

Got a factory 9” 300 blackout barrel off gunbroker for $750, which is a little more marked up from optimal pricing, but with availability being what it is, I’m okay with it.

I have the 16” out for cutting down to 9” as well… I might have that one cut to 11” because the gas block is further towards the muzzle.

[Corse]

Got a factory 9” 300 blackout barrel off gunbroker for $750, which is a little more marked up from optimal pricing, but with availability being what it is, I’m okay with it.

I have the 16” out for cutting down to 9” as well… I might have that one cut to 11” because the gas block is further towards the muzzle.

I have a 16” I was going to cut down to 10”, but for some reason I haven’t done it yet. Probably because they are so expensive.

[JCN]

I have a 16” I was going to cut down to 10”, but for some reason I haven’t done it yet. Probably because they are so expensive.

The local gun shop is asking $80 to cut down. The 16” blackout barrel seems like kind of an oddity in terms of what I’d use it for functionally.

I have a 16” blackout X95 that balances well, a 16” blackout MCX seems like it’d be super nose heavy and unwieldy.

The 16” blackout MCX barrel has a gas block in a different place than a 9” and the 5.5”.

I’m going 11” so I can use the handguard of my 11” 5.56 and just barrel swap.

[JCN]

89466

89467

[JCN]

https://www.sigsauer.com/mcx-virtus-9-caliber-exchange-kit-300blk.html

Still in stock!

[HeavyDuty]

Your results a good bit off what I’ve experienced and seen with the 110 grain Barnes load. Take a look at post 1 and 10 here:

https://pistol-forum.com/showthread.php?26978-Factory-Ammo-Chrono-Results-from-Various-Barrel-Lengths

The Rattler gave up 300 fps to a 9” MCX and came in at around 1825 fps. While this is enough velocity to expand in soft tissue within 25 yards and after many barriers, I’m not surprised that it chokes on soft armor. FWIW, I’ve seen other articles on the load that quote around 1800 fps for the 110 grain Barnes load out of a Rattler and 2100 fps from 9” barrels; none as high as 2K from the Rattler.

I keep coming back to this. My analyst side keeps telling me a second 9” .300 upper with a LVPO would be a good capability extender for my Rattler.

I’m going to be ten minutes away from SIG today, and they have the uppers in stock…

[HeavyDuty]

I keep coming back to this. My analyst side keeps telling me a second 9” .300 upper with a LVPO would be a good capability extender for my Rattler.

I’m going to be ten minutes away from SIG today, and they have the uppers in stock…

… but not in the store, so I ordered one. They did finally have my MCX 11.5” 5.56 upper in, though. Saved me the shipping.

[Corse]

I keep coming back to this. My analyst side keeps telling me a second 9” .300 upper with a LVPO would be a good capability extender for my Rattler.

I’m going to be ten minutes away from SIG today, and they have the uppers in stock…

I’m trying to decide if I need this or not. My legacy MCX has both 16” 556 and 300 barrels, but no option for change unless I have them cut down. I picked up a rattler upper in 300 a while ago. The question is do I spend the coin on a virtus upper, getting access to all the parts/conversions, etc? Or wait for the rumored gen 3.

[vandal]

By the time you will be able to buy a Gen 3 they will have announced Gen 4.

I started getting Virtus upper back in stock notifications a couple weeks after the Gen 3 discussions started trending.


Or wait for the rumored gen 3.

[Corse]

By the time you will be able to buy a Gen 3 they will have announced Gen 4.

I started getting Virtus upper back in stock notifications a couple weeks after the Gen 3 discussions started trending.

You are probably correct.

[HeavyDuty]

I went a little MCX happy before I left NH. I ended up with two Rattler lowers (SBRed and factory pistol) and 5.5” 300, 5.5” 5.56 (my “you go home now” configuration), 9” 300 and 11.5” 5.56 uppers plus different style stocks and braces. Yeesh.

[Corse]

I went a little MCX happy before I left NH. I ended up with two Rattler lowers (SBRed and factory pistol) and 5.5” 300, 5.5” 5.56 (my “you go home now” configuration), 9” 300 and 11.5” 5.56 uppers plus different style stocks and braces. Yeesh.

Crazy might be an understatement. Sig sells the lowers?

[HeavyDuty]

Crazy might be an understatement. Sig sells the lowers?

Nope. I was looking for a second lower to keep in pistol configuration and was made an offer on a new complete 5.56 Rattler that was so cheap that I couldn’t say no.

[JCN]

Dude, have you done much rifle shooting past 100 yards? Because that set up would be a lot of fun out to 300+ yards on steel if you have access to range that goes that far.

Tried this today, mainly just to try it.

Thanks Clusterfrack for the Magnetospeed recommendation, it worked great!

90910

90912


https://youtu.be/--HX85DDBdE

90911

[HeavyDuty]

Tried this today, mainly just to try it.

Thanks Clusterfrack for the Magnetospeed recommendation, it worked great!

90910

90912


https://youtu.be/--HX85DDBdE

90911

Nice! That’s one of your 5.56 uppers, or 300?

[JCN]

Nice! That’s one of your 5.56 uppers, or 300?

It’s my 11.5” Virtus with an AAC can.

I was shooting American Eagle 55gr 223

[vandal]

I'd never shot any .223 through my Virtus until recently... 5.56 milsurp only, never any problems. But recently I've been trying .223 from the bench with 75/77gr bullets to see if I can get better accuracy, which has proven out. Also noticed that the recoil when shooting .223 was virtually nonexistent! Then yesterday I got a click instead of a bang, the bolt was jammed most of the way forward and could not be hammered out with a rubber mallet to the charging handle. I assumed it had tried to load an oversized round.

Got it home and managed to tap it out using a brass punch on the underside of the carrier. Turned out to be a spent case. :confused:

Finally I deduced that the fired round had only enough power to partially cycle the bolt... enough to re-cock the hammer but not far back enough for the case to be ejected, so then the bolt tried to re-chamber the spent case.

And why did it not fully cycle the bolt on firing? Well I can't have a suppressor here so I never really took the time to figure out the gas system... and you guessed it... it had been on the minus setting through about 1500 rounds of 5.56. Not enough force for the .223 rounds I was using.

I'll leave it on + now. :eek:

[JCN]

91002

Did some 100 yard shooting on A zone targets.

So much milder and quieter than the 11.5” lol.

[HCM]

91002

Did some 100 yard shooting on A zone targets.

So much milder and quieter than the 11.5” lol.

Nice. What magwell is that ?

[JCN]

Nice. What magwell is that ?

HRF for $57. It’s a clamp on like a Empire Katana for P365.

https://hrfconcepts.com/collections/front-page/products/rcm-mcx?variant=40448340066493

91028

I like that it’s pretty unobtrusive.

[HCM]

HRF for $57. It’s a clamp on like a Empire Katana for P365.

https://hrfconcepts.com/collections/front-page/products/rcm-mcx?variant=40448340066493

91028

I like that it’s pretty unobtrusive.

Cool

[Default.mp3]

Looks like the Gen3, AKA SPEAR LT, is officially announced: https://www.thefirearmblog.com/blog/2022/09/18/sig-mcx-spear-lt/

https://www.youtube.com/watch?v=Rnh9OCHI_ME

I would be very interested in this gun if I didn't already build my 10.3" with a LAW folder. Oh well, ultimately it's just another 5.56×45mm rifle, and not enough of a leap to even remotely justify replacing my ARs.

[Corse]

I finally got a virtus to replace my legacy mcx and now the new one comes out. At least the parts are backwards compatible this time.

[HeavyDuty]

Does this mean I have to feed my MCX Virtus stuff into a chipper?

94559

[DMCutter]

Does this mean I have to feed my MCX Virtus stuff into a chipper?

94559

No, you can give it to me so you can buy something else new and shiny. I just ordered a PMM MCX BCD and I'll probably spring for a Midwest 12" handguard for my Virtus carbine to shave a little pork to make my own Virtus Lite. If I need something lighter I'll grab the 516.

[HeavyDuty]

SIG sent out an email that the long out of stock collapsing-folding stock is available.

Edit - link: https://www.sigsauer.com/sig-sauer-telescoping-folding-stock-mcx-mpx-blk.html

Edit 2 - cheaper at EuroOptic: https://www.eurooptic.com/STOCK-X-FOLD-TELE-BLK-Sig-Sauer-STOCK--MCX--MPX--SIG-FOLDING.aspx

[JCN]

Hey, maybe an excuse to buy my first 7.62….

[HeavyDuty]

Hey, maybe an excuse to buy my first 7.62….

Rifle seed!

[HeavyDuty]

If anyone is waiting for a 11.5” 5.56 MCX upper, SWFA just got them back in stock: https://www.swfa.com/sig-sauer-mcx-virtus-upper-5-56-nato-11-5.html

[HeavyDuty]

And now Scopelist has the 11.5” 5.56 upper in stock, and the 9” .300:

https://www.scopelist.com/Sig-Sauer-MCX-556-NATO-115-M-LOK-AR-Conversion-Upper-Receiver-w-Tapered-Lug-UAMC.aspx

https://www.scopelist.com/Sig-Sauer-MCX-300-BLK-9-M-LOK-AR-Conversion-Upper-Receiver-w-Tapered-Lug-UAMCX-9.aspx

[HCountyGuy]

So how are these faring overall? Anybody have experience with an 11.5 and suppressor configuration?

[Magsz]

So how are these faring overall? Anybody have experience with an 11.5 and suppressor configuration?

They're very soft shooting. Even with a high backpressure suppressor like a YHM Turbo. I didn't "feel" like my gun was over gassed but I have no way of quantifying that other than going by subjective feel. The gun was very easy to shoot and had a very pleasant recoil impulse.

I find myself replacing my gas rings on most of my bolts at the 4-5k mark on my dedicated suppressed guns. At 2500 rounds through my MCX before it was sold, I didn't really notice anything that would require replacement. Granted, that's not a high round count and I have since sold the gun so I can't really report on anything beyond my own limited experience.

I think once Sig fixes the handguard issue on the spear LT, the guns are going to be exceptional performers over the long haul.

[Mike C]

So how are these faring overall? Anybody have experience with an 11.5 and suppressor configuration?

I have a 16" model Spear LT. It hasn't been run suppressed other than a hand full of rounds with someone else's Sig can. It shoots well and the accuracy seems on par with anything else I've owned in the AR-15 pattern. The Spear LT feels similar the the SR-15 in terms of recoil but that is likely due to the slightly heavier weight. I'm loving the side folding stock and the length of pull on it is probably just about right for most if you're 5'6" or taller. My gun was missing the stupid cheek riser for the skeletonized stock when it arrived. They desperately need them if you run a 1.57" mount anything but I am not a big guy so that may be deferent for others. Over all the gun is running well but I don't have enough rounds through it to really have a strong opinion at this point. One more anecdote. I do have a Surefire XVL2 mounted on mine and it does seem to hold zero 2,000'ish rounds later.

[Sensei]

Just in case anyone decides to spend $2.5k on this rifle only to find a 5 mil zero shift with your PEQ from your hand guard, fear not - Arisaka has got your back like a chiropractor. Their handy dandy $50 solution to you accidentally shooting the hostage will solve all your zero-shift woes.

https://arisakadefense.com/mcx-zero-retention-clamp/

Now, don’t you dare ask why a $2.5k rifle that was supposedly vetted for hard use would need a 3rd party, aftermarket part to make it functional with modern fighting accouterments. Doing so might lead one to suspect that Sig has yet again dumped a steaming pile of dog shit on the market for their customers to step in before a 4th generation rifle is released. Seriously, how the fuck does a company not realize a 5 mil+ shift that is visible to the naked eye just by grabbing the hand guard?

[HCM]

Just in case anyone decides to spend $2.5k on this rifle only to find a 5 mil zero shift with your PEQ from your hand guard, fear not - Arisaka has got your back like a chiropractor. Their handy dandy $50 solution to you accidentally shooting the hostage will solve all your zero-shift woes.

https://arisakadefense.com/mcx-zero-retention-clamp/

Now, don’t you dare ask why a $2.5k rifle that was supposedly vetted for hard use would need a 3rd party, aftermarket part to make it functional with modern fighting accouterments. Doing so might lead one to suspect that Sig has yet again dumped a steaming pile of dog shit on the market for their customers to step in before a 4th generation rifle is released. Seriously, how the fuck does a company not realize a 5 mil+ shift that is visible to the naked eye just by grabbing the hand guard?

SIG was aware for a long time. Like FN with the SCAR non reciprocating charging handles, they’ve had a solution for years. A stiffer handguard they only sold to .MIL/GOV customers.

[Default.mp3]

Just in case anyone decides to spend $2.5k on this rifle only to find a 5 mil zero shift with your PEQ from your hand guard, fear not - Arisaka has got your back like a chiropractor. Their handy dandy $50 solution to you accidentally shooting the hostage will solve all your zero-shift woes.

https://arisakadefense.com/mcx-zero-retention-clamp/

Now, don’t you dare ask why a $2.5k rifle that was supposedly vetted for hard use would need a 3rd party, aftermarket part to make it functional with modern fighting accouterments. Doing so might lead one to suspect that Sig has yet again dumped a steaming pile of dog shit on the market for their customers to step in before a 4th generation rifle is released. Seriously, how the fuck does a company not realize a 5 mil+ shift that is visible to the naked eye just by grabbing the hand guard?Interesting, I thought that the SPEAR LT was suppose to rectify the terrible handguard deflection of the MCX Virtus, as this was allegedly an issue that the regular SPEAR (M7) did not have; IIRC, those screws near the top rear of the handguard was suppose to help with that. I was also told that while the deflection could be very awful, the handguards usually RTZ.

Oh well. Either way, at least there's an aftermarket widget that helps alleviate that issue. Or just succumb to the memes and buy a 500 USD RDS mount.

[Sensei]

Lengthy discussion of this issue on another AR-centric forum. I’ve also seen videos but do not recall if it was the same forum or Reddit. FWIW, lots of commentary about Sig not providing a torque specification for the rear hand guard screws. Some people are reporting >40 in-lbs and still getting visible shift. The Arisaka product does seem to essentially eliminate the problem to the extent that an average shooter does not notice nor can it be accurately measured with calipers.

Still, this is enough for me to hard pass for the time being.

[HeavyDuty]

So how are these faring overall? Anybody have experience with an 11.5 and suppressor configuration?

Ask me in nine months when my can is out of jail. I have four uppers, three are suppressible - 5.5” .300, 9” .300 and 11.5” 5.56.

[HCM]

Lengthy discussion of this issue on another AR-centric forum. I’ve also seen videos but do not recall if it was the same forum or Reddit. FWIW, lots of commentary about Sig not providing a torque specification for the rear hand guard screws. Some people are reporting >40 in-lbs and still getting visible shift. The Arisaka product does seem to essentially eliminate the problem to the extent that an average shooter does not notice nor can it be accurately measured with calipers.

Still, this is enough for me to hard pass for the time being.

It’s a real issue with the first and second generation MCX. As I mentioned, Seguin found a solution in the form of a different hand guard design but in typical SIG fashion, they provided to institutional customers, but didn’t offer it for sale commercially.

Regardless, it’s no longer an issue with the current SPEAR / 3rd gen MCX.

[HCM]

Interesting, I thought that the SPEAR LT was suppose to rectify the terrible handguard deflection of the MCX Virtus, as this was allegedly an issue that the regular SPEAR (M7) did not have; IIRC, those screws near the top rear of the handguard was suppose to help with that. I was also told that while the deflection could be very awful, the handguards usually RTZ.

Oh well. Either way, at least there's an aftermarket widget that helps alleviate that issue. Or just succumb to the memes and buy a 500 USD RDS mount.

The SPEAR LT did rectify it. SIG actually rectified prior to the SPEAR. They produced a solution for certain institutional customers of the gen 1/2 but never offered it commercially. Or at least not till they incorporated it into the SPEAR LT Design.

[UNK]

So, I'm a fan of the MCX when in its intended configuration as a 300blk SBR. Here is mine:
16835

Without the suppressor, the minimum folded length is just 20". That is 4" smaller than my 9" BMC upper on a CMT UMP-PDW that I reviewed here:

https://pistol-forum.com/archive/index.php/t-22028.html

It produces 1" groups at 50 yards using an Aimpoint T2 and Barnes 110 grain VOR-TX (TAC-TX black tips) and is reliable with 1200 rounds in this SBR configuration.

For those of you who plan to replace the factory trigger - be careful. There are multiple bolt carrier assemblies out there, and not all are are compatible with after market triggers. The new "G" marked carriers with a firing pin safety will work with the Geissele SSA. The ALG ACT and stock trigger will function in the "non-G marked" carriers. Others may be hit or miss.

Which one do you like better and why?

[Sensei]

My Rattler is my favorite simply due to size. A MP5K in a rifle caliber is a beautiful thing. Zero drift is a non-issue because the hand guard is so small that you really can’t mount anything to it other than a flashlight. Well, you can but it’s not kinda defeats the purpose.

[Sensei]

HCM

It is an issue with civilian Spear LTs as well which most consider to be 3rd generation.

[MountainRaven]

The SPEAR LT did rectify it. SIG actually rectified prior to the SPEAR. They produced a solution for certain institutional customers of the gen 1/2 but never offered it commercially. Or at least not till they incorporated it into the SPEAR LT Design.

Persons on other forums are reporting significant deflection on handguard-mounted IR/visible lasers with Spear-LTs. It seems to be fixed by increasing the torque on the handguard screws and not all guns seem to be affected by it (with some being affected more modestly than others).

So, if the Spear-LT's handguard is supposed to be the fix, it seems that SIG's QC/QA (or lack thereof) for their commercial products mean that it's not a 100% fix.

[HCM]

Well it appears there is a new barrel deflection issue with the SIG SPEAR rifles, at least the longer barrel versions. This affects both the LT and the new large frame . 308 models.

This was first reported by Lucas from T-Rex arms on a 16 inch 556 SPEAR LT. Essentially, if you push the barrel laterally it will deflect and not return to being centered.

https://www.instagram.com/reel/CsmmB6-tnFa/?utm_source=ig_web_copy_link&igshid=MzRlODBiNWFlZA==



https://youtu.be/KYid0Ptin6A



https://youtu.be/yKbdktoq3vA


https://youtu.be/VHwgvWyExLs

A buddy of mine just picked up a 16 inch spear 308, we checked and it has this issue.

My understanding is Lucas from T-Rex arms is fan of the MCX, and he is saying he’s never had this issue with any of his prior generation MCXs including longer barrel models.

[Sensei]

There seems to be two distinct issues - rail shift and barrel shift. Neither is good but the rail shift is probably the easier of the 2 to mitigate or work around. The barrel shift is perplexing because it actually seems worse than prior generations despite the barrel attachment being essentially identical across generations. Both issues are indictments on Sig’s inability to vet platforms before releasing them to the consumer. What will be interesting to see is the extent to which this issue affects military weapons.

[HCM]

There seems to be two distinct issues - rail shift and barrel shift. Neither is good but the rail shift is probably the easier of the 2 to mitigate or work around. The barrel shift is perplexing because it actually seems worse than prior generations despite the barrel attachment being essentially identical across generations. Both issues are indictments on Sig’s inability to vet platforms before releasing them to the consumer. What will be interesting to see is the extent to which this issue affects military weapons.

The SPEAR rail isn’t shifting but the barrels are on commercial guns.

AFAIK this only affects commercial guns.

My guess this will turn out to be SIG going cheap on either the clamp and/or the fasteners on commercial guns. Either they chose cheaper hardware thinking it was good enough vs .GOV guns (which SIG has a history of doing) or they went cheap on the supplier and got a bad batch of parts (which has also occurred with other SIG products).

[Clusterfrack]

The SPEAR rail isn’t shifting but the barrels are on commercial guns.

AFAIK this only affects commercial guns.

My guess this will turn out to be SIG going cheap on either the clamp and/or the fasteners on commercial guns. Either they chose cheaper hardware thinking it was good enough vs .GOV guns (which SIG has a history of doing) or they went cheap on the supplier and got a bad batch of parts (which has also occurred with other SIG products).

This thread makes me feel even better about divesting myself of Sigs, and not buying any more despite how "cool" the designs appear.

[MickAK]

This thread makes me feel even better about divesting myself of Sigs, and not buying any more despite how "cool" the designs appear.

Garbage is the price of innovation.

[Sensei]

When it comes to the commercial Spear LT rifles, some absolutely do have rail shift. I know this because I have in my possession a 16” Sig Spear LT with a small amount of rail shift that was eliminated by 2 Arisaka ZRCs. I probably could have gotten away with 1 but 2 defiantly did the trick.

When it comes to the commercial .308 rifles, there are ample reports of both barrel AND rail shift floating around but I do not (and will not) have personal experience with this rifle…at least not until Sig gets their shit together.

[HCM]

When it comes to the commercial Spear LT rifles, some absolutely do have rail shift. I know this because I have in my possession a 16” Sig Spear LT with a small amount of rail shift that was eliminated by 2 Arisaka ZRCs. I probably could have gotten away with 1 but 2 defiantly did the trick.

When it comes to the commercial .308 rifles, there are ample reports of both barrel AND rail shift floating around but I do not (and will not) have personal experience with this rifle…at least not until Sig gets their shit together.

I’m not talking about the laser zero issue.

I’m talking about the people claiming that the lateral barrel shift issue is really rail shift and the the barrel is not actually moving.

I have seen this first on both the SPEAR LT 5.56 16” and my buddy’s SPEAR 308 16”

[HCM]

This thread makes me feel even better about divesting myself of Sigs, and not buying any more despite how "cool" the designs appear.

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[WobblyPossum]

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I wonder that myself sometimes. For us, I’m guessing their ability to offer a complete system from a single manufacturer played a big role. P320s, P365Xs and XLs for the UCs and upper management, MPXs, Romeo 1 Pros for the P320s, Romeo 4Ts for the long guns, Romeo Zeroes for the P365s, suppressors for the MPXs, etc. It probably greatly simplifies logistics. I don’t even have a guess about all the military contracts because those are all separate. They didn’t award a contract for a system, they awarded contracts for handguns, contracts for rifles, contracts for LPVOs, etc.

[Sensei]

https://www.reddit.com/r/ar15/comments/14b5b1z/sig_sauers_response_to_my_barrel_movement_unreal/?utm_source=share&utm_medium=ios_app&utm_name=ioscss&utm_content=3&utm_term=1

Sig Sauer’s response to the issue of barrel deflection is that most of the movement originates from the handguard. Otherwise, the small amount of barrel deflection caused by manual distortions is within spec for the intended uses of the gun.

Basically, nothing to see here.

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However, it reaffirms what I’ve been saying. There are 2 separate issues: handguard and barrel movements.

[Up1911Fan]

Has this barrel deflection issue been resolved on the SPEAR LT's?

[HCM]

Has this barrel deflection issue been resolved on the SPEAR LT's?

Define “resolved.”

9 hole reviews and other report that if they deflect the barrel on a 16” gun the first round will be with in 3 inches of POA for the first shot and the barrel will then re-center itself and return to zero for subsequent shots.

Most reports indicate barrel deflection is not an issue with shorter barrels like the 11.5” 5.56 guns.

[Up1911Fan]

Define “resolved.”

9 hole reviews and other report that if they deflect the barrel on a 16” gun the first round will be with in 3 inches of POA for the first shot and the barrel will then re-center itself and return to zero for subsequent shots.

Most reports indicate barrel deflection is not an issue with shorter barrels like the 11.5” 5.56 guns.

Resolved as in can I not move the barrel around with finger pressure. 11.5" is mainly what i'm looking at. Possibly a 16" later on.

[GJM]

I have relatively new 5.56 and 7.62 x 39 11.5 MCX LT uppers. I haven’t shot groups beyond zeroing at 50, but haven’t noticed anything odd about the first shot.

Is this something I am likely to encounter with 11.5 uppers and under what circumstances?

[breakingtime91]

I have relatively new 5.56 and 7.62 x 39 11.5 MCX LT uppers. I haven’t shot groups beyond zeroing at 50, but haven’t noticed anything odd about the first shot.

Is this something I am likely to encounter with 11.5 uppers and under what circumstances?

I have mostly seen it in videos on the 16 inch spear lt but, it could extend to the 11.5. A couple of good youtube videos on it but basically the worry is you could fall in the field the barrel could get impacted creating a shift in zero you wouldn't be aware of. Same way you have to worry about optics after a bad spill.

[HCM]

I have relatively new 5.56 and 7.62 x 39 11.5 MCX LT uppers. I haven’t shot groups beyond zeroing at 50, but haven’t noticed anything odd about the first shot.

Is this something I am likely to encounter with 11.5 uppers and under what circumstances?

No.

Even with the 16" guns there is no deflection unless you mess with the barrel.

As noted, above the 11.5' guns haven't demonstrated this issue at all.

I'm planning on picking up an 11.5' MCX LT 5.56 to replace the 16" I had but the decision to go 11.5 has more to do with weight distribution (front heavy) when fully equipped with a can, light etc than the barrel drama.

[Up1911Fan]

No.

Even with the 16" guns there is no deflection unless you mess with the barrel.

As noted, above the 11.5' guns haven't demonstrated this issue at all.

I'm planning on picking up an 11.5' MCX LT 5.56 to replace the 16" I had but the decision to go 11.5 has more to do with weight distribution (front heavy) when fully equipped with a can, light etc than the barrel drama.


The 11.5" is what I'm looking at too, although I noticed a 9" LE gun as well. More compact is better but I'm wondering what the trade would be as far as reliability and terminal performance. My current load is the 64gr Gold Dot.

[Up1911Fan]

So I have a 9" 5.56 on the way. Need a brace. Is the Sig side folding brace a good option, or does the brace still suffer from the spinning issue?

[Sensei]

https://youtu.be/s6efiG_1b7A?si=nlFFnlpn4zpy_4E9

https://youtu.be/DbGSbZ4X40g?si=zesbPzxy3Wq15Ybg

[HeavyDuty]

So I have a 9" 5.56 on the way. Need a brace. Is the Sig side folding brace a good option, or does the brace still suffer from the spinning issue?

Did you find a solution? A lot of people talk about tightening down the rear screw and sometimes adding friction various ways.

[HCM]

The 11.5" is what I'm looking at too, although I noticed a 9" LE gun as well. More compact is better but I'm wondering what the trade would be as far as reliability and terminal performance. My current load is the 64gr Gold Dot.

If I needed or wanted something more compact I’d be looking at .300 BO.

Sub 10” 5.56 is a non starter for me. While the MCX may address the reliability issues that a sub 10 inch DI gun would have, the blast and loss of terminal performance is unacceptable.

[Up1911Fan]

Did you find a solution? A lot of people talk about tightening down the rear screw and sometimes adding friction various ways.

Ended up with the slim side folding bugger tube with an SBA3.

[Up1911Fan]

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[Up1911Fan]

Finally got out and got the Aimpoint Micro zeroed on the 9" 5.56 Spear LT. After zeroing and running some drills with 55gr FMJ I got back on the bench to determine where I wanted it zeroesd with my defensive load of choice, 64grGold Dots. I shot several groups and made small adjustments at both 25 and 50. This is what I settled on. There are 5 Gold Dots under each of those 1" target pasters. For a 9" braced, folding "pistol", I'll happily take it.
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[HCM]

Finally got out and got the Aimpoint Micro zeroed on the 9" 5.56 Spear LT. After zeroing and running some drills with 55gr FMJ I got back on the bench to determine where I wanted it zeroesd with my defensive load of choice, 64grGold Dots. I shot several groups and made small adjustments at both 25 and 50. This is what I settled on. There are 5 Gold Dots under each of those 1" target pasters. For a 9" braced, folding "pistol", I'll happily take it.
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Curious what the 55 grain groups looked like.

IME accuracy wise the 16" MCX's show a strong preference for heavier bullets.

[Up1911Fan]

Curious what the 55 grain groups looked like.

IME accuracy wise the 16" MCX's show a strong preference for heavier bullets.

I didn't take any pics of them but the groups were pretty similar, maybe a 1/4" + wider spread.

Disregard the pic, that was shot with the Gold Dots.

[vandal]

That has been my experience as well, although it has improved over the MCX -> Virtus -> SPEAR LT generations.



IME accuracy wise the 16" MCX's show a strong preference for heavier bullets.

[Up1911Fan]

One thing I just put together is in each of those 5 shot groups, 4 rounds are pretty tight with 1 slight flyer. I'll have to check into that further next time to try and determine if that's the first round fired.

[Sensei]

Picked-up and 11.5” 5.56 Spear-LT pistol. Slapped a brace and Aimpoint CompM4 on it and hit the range. First 25 rounds were 55 grain XM193 to zero irons at 25 meters. Then, I put another 10 rounds of XM193 to rough zero the optic at 50 meters before switching over to 64 grain Winchester Ranger 556B to fine tune my 50 meter zero. The gun shoots 1.5” 5-round groups at 50 meters using just a CompM4 off a sandbag; addition of a 6X magnifier only marginally improves accuracy at 50M due to enlargement of the reticle over the target. The target on the left was without a suppressor; the right is with a Surefire SOCOM RC2.

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Notice the 3” of downward shift from zero caused by the can at 50M. No feeding or extraction issues. The gun failed to lock-back 2 out of 3 mags with the suppressor attached shooting the RA556B (gas setting on minus). It locked back every time when fired unsuppressed on minus. I suspect the gun is still over-gassed when suppressed even on the minus setting resulting in lock-lack failures due to excessive bolt speed. I’ll play with it some more using a different mag when I get a chance.

[LittleLebowski]

I was made an offer I couldn’t refuse on a 5.56 Spear LT 16” upper and now I’m thinking I need the lower, ‘cause reasons. Watch this space. Got the Arisaka unit on the way already.

https://arisakadefense.com/mcx-zero-retention-clamp/

[HeavyDuty]

I was made an offer I couldn’t refuse on a 5.56 Spear LT 16” upper and now I’m thinking I need the lower, ‘cause reasons. Watch this space. Got the Arisaka unit on the way already.

https://arisakadefense.com/mcx-zero-retention-clamp/

I was just coming here to post about the Arisaka clamp. I noticed my pre-LT 9” .300 and 11.5” 5.56 uppers were pretty easy to deflect with robust slinging, and just installed the clamps on both this morning. They stiffened up considerably (phrasing.)

[crosseyedshooter]

I suspect the gun is still over-gassed when suppressed even on the minus setting resulting in lock-lack failures due to excessive bolt speed.

This is interesting as I recall something from Larry Vickers about the development of the MCX and high bolt speed being an inherent design issue. Geissele won't warranty their regular AR triggers in the MCX because of the bolt speed coming back on the trigger while SIG sells upper kits that can be slapped onto any AR lower. I'm really surprised that there hasn't been more information regarding this online.

[LittleLebowski]

This is interesting as I recall something from Larry Vickers about the development of the MCX and high bolt speed being an inherent design issue. Geissele won't warranty their regular AR triggers in the MCX because of the bolt speed coming back on the trigger while SIG sells upper kits that can be slapped onto any AR lower. I'm really surprised that there hasn't been more information regarding this online.

I’ve seen some chatter about non SIG triggers getting beat up by a Spear Lt.

[Sensei]

This is interesting as I recall something from Larry Vickers about the development of the MCX and high bolt speed being an inherent design issue. Geissele won't warranty their regular AR triggers in the MCX because of the bolt speed coming back on the trigger while SIG sells upper kits that can be slapped onto any AR lower. I'm really surprised that there hasn't been more information regarding this online.


I’ve seen some chatter about non SIG triggers getting beat up by a Spear Lt.

The MCX has a sordid history with aftermarket triggers dating back to the 2016 voluntary safety upgrade of the firing pin block. I managed to get an ALG ACT running in a Gen 2 MCX that has the “G” firing pin block. All of my other MCX rifles have stock triggers which have so far been very good and acceptable on a SDM-type rifle.

Having said that, I suspect that the entire MCX line of rifles is over-gassed. This includes the 308 version of the MCX Spear. Time will tell if it applies to the M7 (.277 Fury) as Sig appears to have been tinkering with the design even in the past year (notice the recent deletion of the forward assist).

[LittleLebowski]

I’m really digging this rifle, it was zeroed so well from the factory that I was banging on steel today at 200 from the standing with the unfucked-with factory red dot and my SIG SRD556 Ti can. Yes, I haven’t touched any adjustments on the RDS, the rifle is minute of man out to at least 200 from the factory with the untouched factory red dot and my SIG can I already had.

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[LittleLebowski]

Greg Bell

[Greg Bell]

Greg Bell

Why are you aways tricking me into spending money??

[LittleLebowski]

Why are you aways tricking me into spending money??

I’m working on side by side impressions of the Caracal and SPEAR in order to save you the expense of buying both 🤣

[Coal Train]

I’m working on side by side impressions of the Caracal and SPEAR in order to save you the expense of buying both 🤣
I am looking forward to this comparison!

[LittleLebowski]

https://jbddesigns.com/products/omega-valve-mod-1-5-56

[MountainRaven]

https://youtu.be/SCVIQVBRgqU

Jonathan Ferguson, Keeper of Firearms and Artillery at the British Royal Armouries Museum, talks SIG MCX in UK LE and military service.

[DMCutter]

https://jbddesigns.com/products/omega-valve-mod-1-5-56

I'm in for one. Cheaper than a flow-thru can.