Short(er) Barrel 6.5 Creedmoor?

[El Cid]

Has anyone messed around with 6.5 Creedmoor in shorter barrels? Most of the options I see are 18 inches and longer. There are some 16” options, but the only one below that I can find is a 14.1” from Ballistic Advantage. I’m toying with a build that would be on the shorter side. Most likely a pin and weld since going the NFA route means it can’t leave the state without a permission slip. I don’t have anywhere to shoot really long distance anyway, and if I did I could always build an upper with a longer barrel.

Everything I’ve read says that 6.5CM from a 14.5 or 16” barrel still outperforms .308 from longer barrels. This is a long-term project so maybe I just wait and let the market catch up? BA certainly makes nice barrels, but I like having options and would prefer a factory barrel over having one cut down.

Thoughts? Anything I’m missing?

Thanks!

[Skinner Precision, LLC]

Has anyone messed around with 6.5 Creedmoor in shorter barrels? Most of the options I see are 18 inches and longer. There are some 16” options, but the only one below that I can find is a 14.1” from Ballistic Advantage. I’m toying with a build that would be on the shorter side. Most likely a pin and weld since going the NFA route means it can’t leave the state without a permission slip. I don’t have anywhere to shoot really long distance anyway, and if I did I could always build an upper with a longer barrel.

Everything I’ve read says that 6.5CM from a 14.5 or 16” barrel still outperforms .308 from longer barrels. This is a long-term project so maybe I just wait and let the market catch up? BA certainly makes nice barrels, but I like having options and would prefer a factory barrel over having one cut down.

Thoughts? Anything I’m missing?

Thanks!

Bolt gun=no problems. Gas gun = challenges and compromises. If your gun plumber makes the challenge/compromises work, you will end up with wicked port erosion at a relativelyly low round count. 6.5 creeds run hotter than 308 win and the port pressures are significantly higher.

I would recommend sticking to 16" minimum in a creed but the heart wants what the heart wants...

[El Cid]

Bolt gun=no problems. Gas gun = challenges and compromises. If your gun plumber makes the challenge/compromises work, you will end up with wicked port erosion at a relativelyly low round count. 6.5 creeds run hotter than 308 win and the port pressures are significantly higher.

I would recommend sticking to 16" minimum in a creed but the heart wants what the heart wants...

That’s not even something that was on my radar - thanks! So 16” gas guns are good to go? Part of wanting to go short is that it will have a can on it.

[Skinner Precision, LLC]

That’s not even something that was on my radar - thanks! So 16” gas guns are good to go? Part of wanting to go short is that it will have a can on it.

16" you can "get by" with a rifle length gas system. 14.5" is going to force you to an intermediate system. Even 20/22" creeds sometimes have trouble with the pressure of Hornady factory ammo depending on how they are set up. Dwell Time , Port Pressure and Peak Pressure all play in the balancing act I mentioned above. 16" isn't a drama free equation but 14.5" gets you more drama and a narrower operating window. I am getting ready to spin a dedicated short range hunter AR 10 creed barrel for myself from a low mile tikka takeoff, it will have a can and I can do my own pin and weld but I am taking my own advice and keeping it 16". Note since it is essentially a free barrel to me, I don't care about the port erosion and if the barrel is trashed before it is shot out... If short/suppressed is driving the mission, I would look at 308 with a 13.7-14.5" 308 Win my biggest concern would be- is if the can I use is rated for it, a lot of "legacy" cans were only rated for 16" and it impressive how much the uncorking pressure goes up as the barrel gets short, IRC 26" is under 2KSI but 16" is around 10KSI

[El Cid]

16" you can "get by" with a rifle length gas system. 14.5" is going to force you to an intermediate system. Even 20/22" creeds sometimes have trouble with the pressure of Hornady factory ammo depending on how they are set up. Dwell Time , Port Pressure and Peak Pressure all play in the balancing act I mentioned above. 16" isn't a drama free equation but 14.5" gets you more drama and a narrower operating window. I am getting ready to spin a dedicated short range hunter AR 10 creed barrel for myself from a low mile tikka takeoff, it will have a can and I can do my own pin and weld but I am taking my own advice and keeping it 16". Note since it is essentially a free barrel to me, I don't care about the port erosion and if the barrel is trashed before it is shot out... If short/suppressed is driving the mission, I would look at 308 with a 13.7-14.5" 308 Win my biggest concern would be- is if the can I use is rated for it, a lot of "legacy" cans were only rated for 16" and it impressive how much the uncorking pressure goes up as the barrel gets short, IRC 26" is under 2KSI but 16" is around 10KSI

Thanks! I already have a 16” 308 gasser. I’ve wanted to try out 6.5CM for a while and snagged a large frame receiver set this past weekend.

Good to know about the cans. My plan was just to use a HUX flow through can. Have those had the same issues? Hopefully the gas venting out the front alleviates some of the concern?

[Skinner Precision, LLC]

Thanks! I already have a 16” 308 gasser. I’ve wanted to try out 6.5CM for a while and snagged a large frame receiver set this past weekend.

Good to know about the cans. My plan was just to use a HUX flow through can. Have those had the same issues? Hopefully the gas venting out the front alleviates some of the concern?
By uncorking pressure I am referring to the pressure of the gas at the end of the muzzle, the longer the barrel- the more opportunity for the gas to be consumed in the barrel- it's why 7.5" 5.56 are so "blasty", the pressure at the muzzle is more. It is a function of barrel length.

I am unfamiliar with an easy way to measure the pressure at the muzzle beyond estimating it via software simulation, quickload being one of the cheapest /most availibleto the average person.

Any can needs to be a strong enough pressure vessel to contain the pressure (hopefully with a comfortable safety factor) and made of materials that resist the abrasive of the hot gas/unhurt powder.

A flow through can like the the HUX reduces the backpressure of gas vented back through the action as it cycles. Even though we callnit backpressure as an analogy to ICE it is really a gas volume not a pressure issue

[JRB]

I'm really curious what you mean by 'outperforms' when you say that a short 6.5 Creed 'outperforms' .308 from shorter barrels.

By all my experience and understanding, 6.5CM is much happier and optimized for longer barrels for the sake of cartridge efficiency. A narrower projectile like the 6.5CM needs more time (read: barrel length) to take advantage of its higher pressures vs a .30 cal.

If you were hot and bothered for SBR length barrels I can't imagine a worse cartridge than 6.5CM to set up for - with the possible exception being that 6.5CM loads are generally very consistent so if you do get something dialed in to run on a narrow operating window, chances are much higher that your gun will run with a variety of ammo.

But if I'm doing an AR-10ish SBR, I'm going .308/7.62 NATO down to about 12.5in at most. Any shorter than that and I'll just do .300 BO or 7.62x39 instead and enjoy much less recoil and muzzle flash for near-as-makes-no-difference terminal ballistics.

6.5CM? I wouldn't bother with less than 20in, let alone 16in. Kneecapping a flat shooting high velocity high pressure cartridge with a too-short barrel is just a recipe for mediocrity.

[texag]

I'm really curious what you mean by 'outperforms' when you say that a short 6.5 Creed 'outperforms' .308 from shorter barrels.

By all my experience and understanding, 6.5CM is much happier and optimized for longer barrels for the sake of cartridge efficiency. A narrower projectile like the 6.5CM needs more time (read: barrel length) to take advantage of its higher pressures vs a .30 cal.

If you were hot and bothered for SBR length barrels I can't imagine a worse cartridge than 6.5CM to set up for - with the possible exception being that 6.5CM loads are generally very consistent so if you do get something dialed in to run on a narrow operating window, chances are much higher that your gun will run with a variety of ammo.

But if I'm doing an AR-10ish SBR, I'm going .308/7.62 NATO down to about 12.5in at most. Any shorter than that and I'll just do .300 BO or 7.62x39 instead and enjoy much less recoil and muzzle flash for near-as-makes-no-difference terminal ballistics.

6.5CM? I wouldn't bother with less than 20in, let alone 16in. Kneecapping a flat shooting high velocity high pressure cartridge with a too-short barrel is just a recipe for mediocrity.

When do the advantages of a 6.5 creedmoor vs a .308win (shooting higher bc bullets at greater velocity with less recoil) disappear? Do they disappear at all?

[SecondsCount]

Why not just build a 6.5 Grendel?

I don't have one but shoot with a couple guys that do. One of them has a 12" barrel, and it does really well.

[Skinner Precision, LLC]

I'm really curious what you mean by 'outperforms' when you say that a short 6.5 Creed 'outperforms' .308 from shorter barrels.

By all my experience and understanding, 6.5CM is much happier and optimized for longer barrels for the sake of cartridge efficiency. A narrower projectile like the 6.5CM needs more time (read: barrel length) to take advantage of its higher pressures vs a .30 cal.

If you were hot and bothered for SBR length barrels I can't imagine a worse cartridge than 6.5CM to set up for - with the possible exception being that 6.5CM loads are generally very consistent so if you do get something dialed in to run on a narrow operating window, chances are much higher that your gun will run with a variety of ammo.

But if I'm doing an AR-10ish SBR, I'm going .308/7.62 NATO down to about 12.5in at most. Any shorter than that and I'll just do .300 BO or 7.62x39 instead and enjoy much less recoil and muzzle flash for near-as-makes-no-difference terminal ballistics.

6.5CM? I wouldn't bother with less than 20in, let alone 16in. Kneecapping a flat shooting high velocity high pressure cartridge with a too-short barrel is just a recipe for mediocrity.


If you stick to 140-147 class bullets I would agree that there is 350-400ish penalty from docking a barrel from 26-16" but if you stay with the 130 gr class of bullets' you only see a 200-250 fps deficit and you still have a bullet with more bc (130 SMK-.584, 130 ELD-M ..279 G7& berger 130 OTM .287 G7) than all but the heavy class of 30cal projectiles, way faster than a shorty .308 can throw them( 185 gr. Jugg to 200 gr low drag/high BC bullet). 16" 130 gr 6.5 @ 2650ish vs 185 gr 16"308 at 2350 is a closer comparison of the two cartridges performance envelope in a short barrel, and the 6.5 does it with less recoil.

My personal PRS rifle (.260 Rem) has a 29" Mueller on it , my boy's more dual purpose 6.5 creed has a 22" Lilja, what you are doing with it drives the choices that budget and availability do not.

The attached picture is what started out as a 24" Tikka CTR in 6.5. It belongs to client who is a serious coyote caller / hunter, he first had me chop his CTR after getting a can and disliking it in the field- he hunted with it for the rest of the season, loved the less then a KY Long Rifle feeling. Before the next season he got a hankering for something fancier so I put a new stock, trigger and carbon fiber wrapped Bartlien barrel on it , he could have had anything from 16-26" without much of a delta in the weight department. After having hunted this rifle at both 24" and 16.5" he choose 16.5" for the Bartlien without hesitation. Convenience for the 5-10 miles of walking he does per day hunting and calling far outweighed the ballistic advantage in this part of the midwest where 450-500 yd coyote shots are about the normal max.

[ST911]

PRS/comp stuff not my lane.

Other folks using 6.5 creed are all 18-20", ala MRGG. I don't know what "outperforms" means, but .308s and creeds running alongside each other are distinguished more by shooter than anything else. Anecdotally, I think the creed is "easier", if you can accept the shorter barrel life.

[Default.mp3]

FWIW, @Failure2Stop (https://pistol-forum.com/member.php?u=1248) said over on M4C:

A 16" 6.5 Creedmoor barrel significantly out-performs a 20" .308 barrel.
I have been shooting "short" 6.5 barrels for about 4 years now. I think that they shine in the 16" area and over 20".
All depends on your application.


Source: https://www.m4carbine.net/showthread.php?236196-16%94-6-5-Creedmoor-barrel-worth-it&p=3040153#post3040153

[El Cid]

FWIW, @Failure2Stop (https://pistol-forum.com/member.php?u=1248) said over on M4C:

A 16" 6.5 Creedmoor barrel significantly out-performs a 20" .308 barrel.
I have been shooting "short" 6.5 barrels for about 4 years now. I think that they shine in the 16" area and over 20".
All depends on your application.


Source: https://www.m4carbine.net/showthread.php?236196-16%94-6-5-Creedmoor-barrel-worth-it&p=3040153#post3040153

Thanks for posting that! Jack is who I was referencing but I couldn’t find the comments so I kept it vague. I also remember something about the 14.5 or 16” 6.5CM staying supersonic longer than 24” barreled 308. But I may be misremembering. lol!

[Nephrology]

I have a 20" 6.5 CM (cut down from 24) bolt gun that I am very happy with. Bolt gun on the left.

https://i.imgur.com/3gYOJ5t.jpg

[Clusterfrack]

I have a 20" 6.5 CM (cut down from 24) bolt gun that I am very happy with. Bolt gun on the left.

https://i.imgur.com/3gYOJ5t.jpg

I like the hospital green wrap on the scope.

[GyroF-16]

I like the hospital green wrap on the scope.

I noticed that too.
Nephrology - what’s the function of the tape, other than camouflage?

[ccmdfd]

I noticed that too.
Nephrology - what’s the function of the tape, other than camouflage?


Chicks dig it!

[Nephrology]

I noticed that too.
Nephrology - what’s the function of the tape, other than camouflage?

Protects vs scratches. And chicks dig it.


I like the hospital green wrap on the scope.

It's actually supposedly british army equipment tape (https://www.amazon.com/First-Only-Airsoft-Scapa-Fabric/dp/B08BLRVSJX) (supposedly)

I do agree its not far off from my scrub suits (I was told the name for that color at our scrub vendor "jungle green" ironically enough)

[El Cid]

For some additional background, I snagged an M5 upper and lower from Aero on Black Friday. I already have a .308 so I was wondering about 6.5CM. I have a preference for walking around size rifles and don’t have a place to shoot beyond 200 yards so a 20+ inch barrel just seems pointless.

[Failure2Stop]

It's actually supposedly british army equipment tape (https://www.amazon.com/First-Only-Airsoft-Scapa-Fabric/dp/B08BLRVSJX) (supposedly)


I don't know if it's the same thing, but we used that tape a LOT when I was working in the UK.

[Failure2Stop]

Has anyone messed around with 6.5 Creedmoor in shorter barrels? Most of the options I see are 18 inches and longer. There are some 16” options, but the only one below that I can find is a 14.1” from Ballistic Advantage. I’m toying with a build that would be on the shorter side. Most likely a pin and weld since going the NFA route means it can’t leave the state without a permission slip. I don’t have anywhere to shoot really long distance anyway, and if I did I could always build an upper with a longer barrel.

Everything I’ve read says that 6.5CM from a 14.5 or 16” barrel still outperforms .308 from longer barrels. This is a long-term project so maybe I just wait and let the market catch up? BA certainly makes nice barrels, but I like having options and would prefer a factory barrel over having one cut down.

Thoughts? Anything I’m missing?

Thanks!

Did I just email you on this topic?
If not, crazy coincidence, but I'll repost here what I recently had to say on the matter:
*NOTE: "MRAD"="MILS", I just prefer the technical accuracy of "MRAD" over "MILS" in writing.
Distances in yards. Projectile weight in grains. Projectile velocity in feet per second.

Comparatively, a 14.5” 6.5mm Creedmoor will show about the same drop correction as a 20” 7.62 shooting 175gr ammo, but with about 1/3 less wind drift inside 800 yds. The 6.5 projectile is also way less affected by trans-sonic (and trans-sonic happens at a further distance), making those longer pokes easier. That’s mostly applicable to those that carry a 20” 7.62 rifle that meets their range requirements, as they can go to a significantly shorter and lighter system and meet or exceed their current performance.
Personally, I really like 16” for 6.5 CM, not only for avoiding NFA hassles, but also for the velocity gain over 14.5” barrels.
Once you go past 16”, I’m just not seeing the benefit to the weight and length until you hit about 22”. With a 22” barrel I will be in the 2750 ft/s area with 140gr Berger AR Hybrid projectiles, which is really the next step up in practical performance over the 2500-2600ish ft/s of the 14.5-16" (projectile and load dependent, of course).

My 16” shooting 140s will show 10 mrad of drop at 1,000 and 2 mrad of wind correction for a 10mph wind from 3:00.
22” will show 8.7 mrad of drop and 1.9 mrad of wind.
20” 7.62 with M118LR will show 11.6 and 2.8
16” 7.62 with M118LR will be 12.8 and 3.0

My 16” is a 5mph gun out to 800 (+.1 at 900 to 1000, +.2 at 1100, and adding an additional .1 sequentially past that)
My 22” is a 5mph gun out to 1,000 (+.1 at 1100 to 1200, increasing by .1 every 100 yards past that)
That 6” of barrel difference is needed to get any useful gain in performance for wind or drop.

When it comes to speed drop, my 16 is 1.8 (covers 300 to 650 with .2 error) 22” is 2.1 (covers 300 to 800 with .2 error).

For ranging error, I’m 0.5 mrad difference between 800 to 835 with 16”, and 800 to 840 with 22”.

For midrange center hold, putting 1.5 mrad on the gun will cover 295-365 with +/-0.3 mrad error with 16”, while 1.3 on a 22” will cover 295-380 with +/- 0.3 error.

For midrange dial/hold patterns; with the 16”, dialing 2.1 mils onto the gun will make the center crosshair 400, 1 mrad will be 500, and 2 mrad will be 600, with a 0.1 error between 400 and 600 –OR- dial 3.1 on and hold under 1 mrad for 400 and over 1 mrad for 600.
22”: dial on 1.8 mrad and center will be 400, 1 mrad=500, 2 mrad=600, 3 mrad=700 with a 0.1 mrad error -OR- dial on 2.8 and hold under 1 mrad for 400, center for 500, 1 mrad for 600, and 2 mrad for 700.

From comparison, the 14.5” 6.5 will be a 4.5 MPH gun to 800 yds, will show about 2.3 mrad of drift from a 10 mph wind at 1,000 yds, speed drop is 1.6 (250 to 520), ranging error is 0.5 mrad difference between 800 and 830, 1.7 dialed on will cover 295 yds to 335 yards (+/-.3), and dialing on 1.5 mrad will give center for 300 yds, 1 mrad hold over for 400 yds, and 2 mrad hold over for 500 yds.

Anyway, at least that’s how I see it.

[El Cid]

Did I just email you on this topic?
If not, crazy coincidence, but I'll repost here what I recently had to say on the matter:


Yessir! I initially couldn't find your email to ask, so I posted here. Thanks for the excellent and detailed response! Any chance you'll start teaching again?

[Failure2Stop]

Yessir! I initially couldn't find your email to ask, so I posted here. Thanks for the excellent and detailed response! Any chance you'll start teaching again?

Hah! Great, I was starting to worry about excessive deja vu experiences.
I come out every now and then to do shooting gooder stuff, I do enjoy seeing people move up to the next level.

[El Cid]

Testing of a 14.5” 6.5CM

https://m.youtube.com/watch?v=2slz2R20qyw&t=316s