Thoughts on the Colt AR6720 Lightweight LE Carbine

[Jay Cunningham]

I intend this to be an ongoing thread on the Colt AR6720 Lightweight LE Carbine - both my own personal gun and hopefully input from others who own and use the gun.

Let's start off with the description from colt6720.com (http://colt6720.com/the-colt-6720):



Designated the Colt AR15-A4, Lightweight LE Carbine, the AR6720 was designed to meet the needs of the law enforcement officer.

In partnership with Colt, it is available exclusively through Clyde Armory Law Enforcement Supply.

Designed specifically for the Law Enforcement patrol officer, its lighter platform recognizes the need to minimize weight while not compromising durability as firearms are generally carried for long periods of time and weight becomes a significant factor. The AR6720 represents a new generation of Colt rifle, which comes standard with an optics ready rail and a flip-up rear iron sight.

Colt’s use of the MaTech flip-up sight is unique among flip-up rear sights in that it has adjustment for both windage and elevation and its slender design allows for maximum peripheral vision when in use giving the shooter the most unobscured view of the target. These are also the reasons that the MaTech flip up rear sight has been the US Military standard for almost a decade.

The 16” standard weight barrel is magnetic particle tested after proofing by Colt to ensure every barrel is made of perfect steel with zero flaws. Because of this tight quality control, Colt barrels are durable enough to handle thousands of rounds of highly accurate semi-auto fire yet maintain a lightweight profile. Its 1:7 twist gives it the flexibility to use the widest range of ammunition from 40 grain varmint rounds to 77 grain long range match, while maintaining ballistic stability.

The bolt head is also magnetic particle tested by Colt to ensure all steel surrounding the cartridge is perfect and without flaw. These extra steps of quality are what set Colt rifles apart from other AR-15 type clones.

The AR6720 is a hybrid of Colt’s Government Carbine model AR6520 and Colt’s Flagship M4 Carbine model LE6920. This Lightweight Law Enforcement Carbine has a new roll mark of AR-15A4 recognizing Colt’s newest designation of an optics ready carbine.


I've only put 50 - 60 rounds of greentip through mine at this stage to confirm function and get a rough 100 yard zero.

[Jay Cunningham]

Some initial musings:

Out of the box, the gun was pretty well slathered in lube... fairly typical for a Colt rifle. It came with a segmented cleaning rod, bore brush, chamber brush, manual, two 20 round black PMAGs (http://store.magpul.com/product/MAG560/PMAG), a black nylon carry strap, and a male QD sling attachment point. This model came with the new Colt Super-Stoc.

The Super-Stoc is a little on the ugly side, but it seems robust and has pretty much the same set of features as the MagPul CTR (http://store.magpul.com/product/MAG310/180). What I couldn't figure out was the inclusion of a conventional sling mount on the bottom of the front sight base. The only real "factory option" for sling installation is to attach at the bottom of the front of the gun but at either the QD point near the bottom side of the stock or perhaps around the top of the stock. This arrangement is unworkable IMO... at the very minimum, Colt should have shipped this gun with a sling mounting option on the front that made more sense. Perhaps Colt considers the carry strap to be a throwaway part, much like they seem to consider the A2 grip? If Colt saw fit to upgrade stocks (the standard M4 stock isn't bad) I can't understand why they don't think it's time to upgrade grips? Something like a MagPul MIAD (http://store.magpul.com/product/MAG520/39) would make a lot more sense, what with all the frontstrap and backstrap options.

The gun is a true M4 flat top (marked at the top front of the upper receiver) but it uses a standard (not "F" marked) front sight base/gasblock. This was always a big criticism of Bushmaster and some other "lower tier" ARs but Colt decided it was fine here. I'm pretty sure an LE6933 FSB would go on this rifle... but maybe I'm just being picky. I've read that Colt installed a taller front sight to compensate for this, but I'm not so sure - I'd need to mike it out.

I removed the M4 handguards and one of the two heatshields on the upper handguard to install two separate Impact Weapon Components accessories: a TMC 1" Light Mount-N-Slot (http://www.impactweaponscomponents.com/product/tmc-1-light-mount-n-slot/) and a TM QD Rotation Limited Sling Mount-N-Slot (http://www.impactweaponscomponents.com/product/tm-qd-rotation-limited-sling-mount-n-slot/). I then installed a Sheriff of Baghdad Weapon B-Sling (http://www.missionreadyequipment.com/sheriff-of-baghdad-b-sling) and a SureFire G2L light.

The rifle comes standard with a MATECH BUIS. It was mounted on the second-to-last rail slot and was loose. I re-mounted it to the rearmost slot and tightened it up. It is spring-loaded and does not lock in the upright position. There is only one aperture, and there is no elevation adjustment. There is a windage knob and there is a range lever. More thoughts on this after I use it more.

The rifle was "on" for windage and about 2.5" low at 25 yards... I like to rough zero my sights for 1.5" low at 25 yards which I've found gets me very close to POA/POI at 100. I set my elevation lever at the shortest range: 200. I needed to adjust my front sight down a bit to bring my group up but it only took a couple of clicks. As I was writing this, I came across an instruction sheet which says for the M4 carbine to use the 300 mark. Meh, I don't know how much of a difference this makes but I'll keep it in mind. Once I set my sights I never adjust them anyway.

The gun was printing quarter-sized groups at 25 yards with iron sights and 62 grain PMC ammo. Trigger was typical (fine) and function was unremarkable. The magazines locked the bolt back each time and both dropped free.

I replaced the horrid A2 grip with a TangoDown BG-17 grip (http://tangodown.com/shop/product_info.php?cPath=21&products_id=134). At some point I may spring for a BCM Gunfighter grip (http://www.bravocompanyusa.com/BCM-GUN-FIGHTER-s-Grip-GFG-Mod-1-Black-p/bcm-gfg-mod-1-black.htm).

The gun is now wearing an old Aimpoint Comp ML2 optic in a factory Aimpoint mount.

Now I get to go to the range and play with it some more. Next stop: confirm iron sights zero at 100 yards and then align the optical sight.

[rob_s]

Any idea when the 6720 was introduced? I know that I bought two 6520s in 2005 or so and swapped one out for a flattop upper because the 6720 wasn't out at the time. I've been thinking of buying a 6720 just to put in the safe for a rainy day ever since they came out, but I can't remember when that was.

Not terribly important, just curious since many of us did the flattop conversion when there was no other choice.

[Jay Cunningham]

Unsure of the exact date Rob... it was sometime in the Spring of 2010 I believe.

[LittleLebowski]

Pondering the worries over the thin barrel heating up, in reality what is an accuracy standard for a home defense/training carbine? I'm thinking 4MOA 5 or possibly 10 shot groups.

[rob_s]

Pondering the worries over the thin barrel heating up, in reality what is an accuracy standard for a home defense/training carbine? I'm thinking 4MOA 5 or possibly 10 shot groups.

The twerp shot a DD LW barrel for groups on TOS. I posted a link in the original lightweight thread.

Completely anectdotal, but my experience has been that I've never missed a shot or lost a match because of my barrel. Or, for that matter, my optic, trigger, stock...

[TGS]

Pondering the worries over the thin barrel heating up, in reality what is an accuracy standard for a home defense/training carbine? I'm thinking 4MOA 5 or possibly 10 shot groups.

I think because so many people like to use their carbine for other things. Or, for that matter, they simply want their carbine to perform as a "proper" carbine should because of principle.

Personally, I also like target shooting with mine. I think if all you plan to do with the gun is shoot someone across the room, then all the complaints about the accuracy of 196-series mini-14s and su-16b carbines is moot. So, I sorta agree with you.

[Little Creek]

I have had a LT6720-R for about 9 months. It came with a 10" Troy quad rail with MBUIS. Is the free floating rail an asset on a LW carbine? The only change I have to this carbine is a MOE grip. It has a Rogers SS. I do like the QR sling swivel capability on the stock as well as on the quad rail, front and rear.

[Chris Rhines]

Is the free floating rail an asset on a LW carbine? For a carbine that will only be used indoors, while standing on one's hind paws, probably not. If you're going to do any kind of position or supported shooting at longer ranges, then yes, it's an asset.

[Chuck Haggard]

Under the handguards the barrel is the same as that of the M4, no? I know it's the same as the M16/M16a1, and I never had an accuracy issue with an a1 unless something was jacked up on the gun.

My Ken Elmore built pre 6720 is all stock Colt parts, but if I use Federal TRU 55gr BTHP or Hornady 60gr TAP, and shoot from prone off of a sand bag rest for my front hand, the gun shoots into 1 1/2. I can get 4-5" from everything I shoot, Tula included. BTW, my HBAR never shot as well as my skinny barrel gun.

[rob_s]

I think because so many people like to use their carbine for other things. Or, for that matter, they simply want their carbine to perform as a "proper" carbine should because of principle.

Personally, I also like target shooting with mine. I think if all you plan to do with the gun is shoot someone across the room, then all the complaints about the accuracy of 196-series mini-14s and su-16b carbines is moot. So, I sorta agree with you.

This is grossly exaggerating the issue as relates to the 6720 or other .650" OD barrels.

if people get pleasure out of shooting for groups at a bench or prone on paper then the LW barrel is probably not ideal for them, but I bet that most of those same people are the primary accuracy issue, not the barrel (or ammo, stock, trigger, etc.). Personally, the first time I shot in a dynamic environment (a carbine match), I was done with bench shooting forever.

[rob_s]

Is the free floating rail an asset on a LW carbine?

IMO and IME, yes and perhaps even more so. Not from a traditional, benchrest, bolt-action "bedding" free-float perspective but from a perspective of shooting in dynamic environments the LW barrel is theoretically more succeptible to movement when braced than a thicker barrel. Therefore the carbine-centric benefit of the free-float holds true for LW barrels because the goal is to isolate the barrel from outside influence when braced. I participate in several events where the 9-hole drill is used extensively and resting a non-free-float barrel on the wall can affect POI even at 50 yards.

[Chuck Haggard]

I recall shooting for groups back in the days of using an M16a1 as an "automatic rifle", as one would a BAR. The only gear or mod for that job was a clip on "clothes pin" type bipod. From prone vs prone crappy bipod the POI would shift upwards 7" or more. I note that using the sling as one would in a high power match would also radically shift POI vs POA. Free float handguards on a light barrel are a very good idea IMHO.

[TGS]

Excellent observations on the free-float handguards. I never realized the POI shift could be that dramatic.

I don't know if you guys remember, but a while back I started a thread about ultra-light carbines, and discussed a .55" barrel. Now that the market is starting to cool down I'm starting to buy piece-by-piece, and I'm glad I've seen this dramatic POI shift mentioned before I invested in the barrel/handguard setup.

[GJM]

My first AR, was a skinny barrel Colt, and the POI shift, when shot slung, was quite large. It took me a while to figure out, and between that, and trying to shoot groups with the large aperture, I had a heck of a time and wasn't impressed with the AR. When the AUG came around, it seemed like cheating by comparison. AR's sure have come a long way since then.

Wasn't the HBAR at least in part to get away from the sling sensitivity of the skinny barrel AR's?

[DocGKR]

The 6720 type AR15's are my favorite Colt carbines. They definitely benefit from a FF rail--I typically add a long rail of 12" or so length. And yes, back when we had M16A1's, it was quite easy to induce shifts of 6-8" at 100 yds simply by resting the barrel on an object, running a bipod, or using a tight sling.

[Sadmin]

I own/use this model as well, and although I never attempted to self-induce a POI shift before it was railed, I error on the side of caution.
That; plus being lanky the 7" handguards dont cut it...even with stock at full extension. The "snappabilitaa" is most noticeable on something like
the vtac triple threat where I make vertical moves rather than horizontal, dont know why, im sure its just me. Great gun though, and it shattered my notion
that carbines are harsh cyclers, its as every bit as smooth as my mid after I put a h3 in there.

http://i7.photobucket.com/albums/y283/r3h4b/IMG_1440-1-1.jpg

[rudy99]

Aw man, you people are making me regret going with the MOE handguard instead of a Centurion rail on my LW BCM middy. If it weren't for the additional cost of the Impact Weapons light mount and QD, I wouldn't feel so "invested" in this option. I figured I wasn't going to use this rifle for any "precision" type of role, so the added cost of a FF handguard would have been wasted. All these threads questioning peoples "need" for a FF handguard with the undertone that they just wanted it because it looked cool pushed me towards the MOE thinking that was the wiser option (that and I consider my rifle to be my secondary). Oh well. I'm sure I'll be fine in the end.

[Jay Cunningham]

Lol,

How about *actually* evaluating the performance of the rifle and *then* determining if the FF thing is important to you?

That's what I'm going to do, anyway.

[LSP972]

I've had mine for about a year now, after the wife decided she wanted one of her own and declared that my trusty old 6520 was EXACTLY what she needed...:rolleyes: I couldn't find a NIB 6520 for less than a king's ransom, and Bud's was offering the 6720 for slightly less than a grand, so...

I replaced that five-pound rear BUIS with a MagPul unit, the communist A2 pistol grip with a proper A1 example, and the oval handguards with by-God genuine small round ones. Bolted on an H1 and a TLR-1, a sling, and its good to go.

With the exception of those making a match gun for 600 yard work, I have never understood the fascination with these porker, stepped heavy barrels. I'm fresh out of both launcher and grenades, so why lug around the extra weight??? The pencil barrel makes all kinds of sense for a general-purpose carbine; to me, anyway.

.

[rob_s]

Lol,

How about *actually* evaluating the performance of the rifle and *then* determining if the FF thing is important to you?

That's what I'm going to do, anyway.

Exactly. While *I* have found that for *my uses* the FF on 0.625" OD barrel makes a difference, someone not shooting braced off of object much may not. Or, may find another workaround that works better for them.

My BCM dissipator (which is a 16", A2 profile barrel with rifle-length handguards) seems much less susceptible to POI shift on the 9-hole for whatever reason.

[rudy99]

Lol,
How about *actually* evaluating the performance of the rifle and *then* determining if the FF thing is important to you?
That's what I'm going to do, anyway.

Sounds like a lot of work, but you may be on to something here.

[Jay Cunningham]

http://img.tapatalk.com/d/13/06/21/any8ebev.jpg

The carbine as pictured (no magazine, empty chamber) weighs 7 lbs. 9 oz.

At 100 yards off of the bench I kept 7 of 10 rounds inside the black of a bull on the obverse of a VTAC target with iron sights. The rounds favored left and the three outside the black were a little high and left; pretty good rough zero at 25 yards. I threw one extra click of right windage in and will check it again next time.

The above was with the Aimpoint detached. I went ahead and stuck it back on and dropped the dot straight down onto the top edge of the front sight, then I folded down the rear and shot a group.

Five rounds hit 4" left. I dialed in some windage and put five for five in the black. I then switched to a 12"x12" steel square at 200 yards. I initially placed my dot on the top edge of the target but wasn't getting results, so I simply held dead center: hit - hit - hit, etc. The old "boring regularity" thing.

So no hard data for this post besides the weight. The carbine functioned just fine and I won't mention function again unless I need to.

So far I'm happy, but more to come.

[ST911]

I got my 6720 in 05/2010 or so, and it was one of the first 500. It came with the Matech sights, two 20rd PMags, H-buffer, and the GI-type stock. When received, I did a quick once over but no detailed inspection. I then lubed it up and threw it in the back of my GOV for about a week. At the end of that week, I fired 2053 rounds in three total hours, over two range sessions (~1300 or so and ~700) without stoppage. Since, it's been to classes, quals, and accrued several thousand more rounds. I changed the bolt rings once, and I think I'm due for an action spring. I've had the same Matech BUIS on it since the beginning, but broke the crossbolt once and replaced it. That's pretty common. I've been running the same T1 (LT mount) as well.

This 6720 is my EDC and duty rifle, and is commonly used as an exemplar in demonstrating and justifying LW rifles for patrol rifle programs. My wee ones, ladies, and IBOs can run it with great effectiveness.

In a recent work-up of differential POIs, an assortment of duty and training loads (most 55gr) all shot within 4" from a monopod prone on a B8 bullseye at 100yds. A few of the better loads with this gun will consistently come in under 2". When heated up, they open up a bit but not as much as you would predict. This included some crappy low end stuff, as well as TulAmmo and Herters-Tula. I did NOT sling up or introduce any barrel stresses or forces. (I'm away from home and can't be more quantitative than that right now.) I do know that I ran a stack of magazines of some 55gr training ammo on steel torsos at 200yds. While the forearm was hot hot hot, I could still hit COM on the torsos without issue. Accordingly, this gun meets my needs. This gun also functions with low-impulse handloads, frangible and green ammo, and some non-commercially available ammo that is iffy in some others.

I have considered a FF and quad rail, but don't have need to mount other tools/accessories. My next modification will be a new light mount and an updated light (Fury), but other than that it will remain as pictured for the foreseeable future.

http://i76.photobucket.com/albums/j18/Skintop911/Colt%20AR6720/6e2aed76.jpg

Someone asked about the barrel profile.

http://i76.photobucket.com/albums/j18/Skintop911/Colt%20AR6720/fdcfbbb3.jpg

[Dan_S]

Skintop,

What light mount are you using on that 6720? (I noticed two different light mounts in your photos actually, and I'm curious which one you recommend at this point.)

[Kyle Reese]

I got my 6720 in 05/2010 or so, and it was one of the first 500. It came with the Matech sights, two 20rd PMags, H-buffer, and the GI-type stock. When received, I did a quick once over but no detailed inspection. I then lubed it up and threw it in the back of my GOV for about a week. At the end of that week, I fired 2053 rounds in three total hours, over two range sessions (~1300 or so and ~700) without stoppage. Since, it's been to classes, quals, and accrued several thousand more rounds. I changed the bolt rings once, and I think I'm due for an action spring. I've had the same Matech BUIS on it since the beginning, but broke the crossbolt once and replaced it. That's pretty common. I've been running the same T1 (LT mount) as well.

This 6720 is my EDC and duty rifle, and is commonly used as an exemplar in demonstrating and justifying LW rifles for patrol rifle programs. My wee ones, ladies, and IBOs can run it with great effectiveness.

In a recent work-up of differential POIs, an assortment of duty and training loads (most 55gr) all shot within 4" from a monopod prone on a B8 bullseye at 100yds. A few of the better loads with this gun will consistently come in under 2". When heated up, they open up a bit but not as much as you would predict. This included some crappy low end stuff, as well as TulAmmo and Herters-Tula. I did NOT sling up or introduce any barrel stresses or forces. (I'm away from home and can't be more quantitative than that right now.) I do know that I ran a stack of magazines of some 55gr training ammo on steel torsos at 200yds. While the forearm was hot hot hot, I could still hit COM on the torsos without issue. Accordingly, this gun meets my needs. This gun also functions with low-impulse handloads, frangible and green ammo, and some non-commercially available ammo that is iffy in some others.

I have considered a FF and quad rail, but don't have need to mount other tools/accessories. My next modification will be a new light mount and an updated light (Fury), but other than that it will remain as pictured for the foreseeable future.

http://i76.photobucket.com/albums/j18/Skintop911/Colt%20AR6720/6e2aed76.jpg

Someone asked about the barrel profile.

http://i76.photobucket.com/albums/j18/Skintop911/Colt%20AR6720/fdcfbbb3.jpg

I like your setup - no BS, no frills. How do you like the ARC mags? I've been very happy with mine, and have found them to be more reliable than the first production run of Lancer Advanced Warfighter Mags. This thread has me pricing 6720's online...... Like I need another AR.....

[ST911]

Skintop,

What light mount are you using on that 6720? (I noticed two different light mounts in your photos actually, and I'm curious which one you recommend at this point.)

They should be the same light and mount? Not sure what other pic you're referencing.

It's a VTAC mount on a rail section, Surefire G2, Malkoff drop in. Cheap, simple, functional. I'm going to look at some other options in mounts, and will almost certainly change that light out to a SF Fury.


I like your setup - no BS, no frills. How do you like the ARC mags? I've been very happy with mine, and have found them to be more reliable than the first production run of Lancer Advanced Warfighter Mags. This thread has me pricing 6720's online...... Like I need another AR.....

I like the ARCs and have great luck with them, including the earliest production. The ones pictured above are v1 and some transitionals.

[Jay Cunningham]

Of all the days to forget to wear my contacts...


I made a quick trip to the range after work today with the sole intention of firing a group from the 6720 and a group from my recce/gamer/whatever rifle under similar circumstances. The temperature was 84 degrees F, the winds were calm, and humidity was 33%. The range faces west and I shot between 1600 & 1700 and was getting glare from the setting sun in my face.

I planted a VTAC target out at 100 yards and shot 10 rounds through the Colt first, with a minimum 30 second interval between shots. Optic was a 4 moa Aimpoint and ammo was generic 62 grain greentip.

I then removed the optic and installed it on my recce/gamer/whatever rifle. This rifle has a BCM barrel with the following characteristics:

Features

M4 Feed Ramp Barrel Extension
Mid Length Gas System
1/8 Twist Rate
5.56 NATO Match Chambers (USMC SAM-R Chamber)
410 Stainless Steel
Mid Weight Contour Profile Barrels
Button Rifled
Hand Lapped Rifling
HPT (High Pressure Test) Barrels
MPI (Magnetic Particle Inspected) Barrels


1572


So, pretty fancy. It also has a Geissele Super Semi-Automatic (SSA) trigger and a DD free float M4 Rail 12.0. So with the exception of the aforementioned gadgetry, I shot the same ammo at the same rate at the same target with the same atmospheric conditions with the same optic off the same benchrest position... I do not "sling up" at the bench.

So here were my results:


Colt 6720 10 round group max spread: 4.875"

Fancy BCM barrel 10 round group max spread: 3.75"


Colt 6720 nine round group (worst "flyer" deleted): 3.5"

Fancy BCM barrel nine round group (worst "flyer" deleted): 3.0"


If you disagree with my methodology, I'm cool with that. I have never been nor will I ever be a numbers guy. I figure as long as my methodology (such as it is) is consistent it should be good enough.

My take away from this was that inside 100 yards with a 4 moa 1x optic and decent (but certainly not match) ammo and a light firing schedule, the actual benefits from fancy barrels, triggers, and free float tubes is minimal. It's there, but maybe you're buying yourself a half moa. I will note that shot group "density" seemed tighter with the BCM barrel. I had three holes touching in this group; the Colt group did not have holes touching.

My next little test will involve a more demanding firing schedule... and also eyewear so I can actually see the damn target. :cool: I also plan on shooting closer to midday to eliminate glare from the sun being in my face.

[GJM]

As long as you are testing, it would be interesting to work 3 things into the mix:

1) some ammo with a rep for shooting well.

2) some magnification to help tease ou what is the rifle/ammo accuracy versus ability to see the target.

3) either slinging or bracing, that might show up the difference between free float and standard hand guards.

[Jay Cunningham]

Yeah I have some of that already planned.

You PF members are so helpful!

;-)

[GJM]

Yeah I have some of that already planned.

You PF members are so helpful!

;-)

Yeah, it is almost as good as being POTUS, having "staff" with ammo and carbines to do your testing, and report back.

[Jay Cunningham]

http://img.tapatalk.com/d/13/06/22/a4uby3yn.jpg

Upper group is from the 6720, lower group from the BCM barreled gun.

[Chris Rhines]

I'll be interested to see some groups from the 6720 with a scope mounted. I suspect that the RDS is probably the limiting factor with regards to accuracy.

[Jay Cunningham]

I suspect you're correct; it only makes sense.

Since none of you can wait, I'll give you my itinerary:

- Repeat the exact same test as above but first dump 20 rounds as fast as I can pull the trigger, and without the 30 second cool down time.

- Repeat the first test exactly but with a 1.75 MOA Trijicon SRS on both guns.

- Repeat the same test at 200 yards with 55 gr. match ammo and an AccuPoint set at 4x.

:-p

[GJM]

and, don't forget your contact lenses.

[Jay Cunningham]

Got my prescription polarized sunglasses on! GTG!

http://img.tapatalk.com/d/13/06/23/y2eruty6.jpg

[Jay Cunningham]

I did the exact same exercise today as yesterday except I used a 1.75 MOA Trijicon SRS on both guns. Weather was the same but more humid.

Colt LW barrel 10 round max spread: 4.375"

BCM barrel 10 round max spread: 4.6875"

Colt LW barrel nine round spread (minus worst "flyer"): 3.25"

BCM barrel nine round spread (minus worst "flyer"): 4.0625"

The Trijicon SRS has a lot going for it, but one of the downsides is that if light hits the front lens a certain way, optical artifacts begin to manifest, which are distracting. I tried shading the front lens with my hand, and lo and behold not only did the artifacts go away but I was also able to lower the intensity to get an even more precise dot. I tried the Colt again this way. Results:

Colt LW barrel 10 round max spread: 3.0625"

Colt LW barrel nine round spread (minus worst "flyer"): 2.625" (!)

I ran out of time so I didn't get to redo the BCM barrel while shading the optic on lower intensity.

I'm pretty impressed with the Colt group. However I haven't done anything yet to take the LW barrel "out of it's comfort zone" and into the territory where the BCM barrel may give a significant advantage.

But I will.

[TGS]

Question, sorry if it's answered in the thread but I haven't seen it:

Is the BCM also a lightweight barrel?

[Jay Cunningham]

They call it a "mid weight contour" but it looks fairly heavy to me.

[Chris Rhines]

They call it a "mid weight contour" but it looks fairly heavy to me. I happened to have the handguard off of my 16" Reece, so I broke out the calipers. From the chamber, the barrel tapers from ~0.850" at the chamber end to ~0.790" at the gas journal, 0.750" at the gas journal, then drops to ~0.730" to the muzzle. It's kind of in-between an HBAR and an -A2 profile.

[Jay Cunningham]

Correction: I had been stating that the dot MOA on the Trijicon SRS is 1 MOA... that is not correct.

The Trijicon SRS has a 1.75 MOA dot.

[BWT]

That is fascinating, thank you for sharing!

Alright, some questions and suggestions.

(Take them or leave them)

1.) Is that a Stainless Steel barrel for the Heavier contour?

2.) Try shooting with the highest magnification optic, I'm thinking that'll reduce the human element further.

Thank you for volunteering your time and bullets!

[Jay Cunningham]

Yes, it's stainless.

I will heat up the guns and shoot them both with a magnified optic.

Note: the Colt LW barrel wears an A2 flash hider and the BCM wears a BattleComp. I'm not testing "controllability" but just wanted to mention it. If I really wanted to get down to it, I could remove the muzzle devices.

[Kyle Reese]

I'm currently trying to convince a colleague to purchase the 6720 in lieu of the 6920 SOCOM. For range work, I'm not seeing any real benefit to the heavy barrel, and the 6720 will cover his needs just fine (plinking and range work at 100 yards and under).

[BWT]

Alright sir, I've got another question for you.

In the other thread you posted a picture of an LE6933 as a lgihtweight Carbine in jest.

I'm genuinely curious, what would a stripped down (or similarly equipped) 11.5'' upper weigh versus the 6720 upper versus a standard 6920 upper.

I obviously realize you may be limited to what you have access to, but, maybe if any of you have one of these items, you can chime in, and from the conglomerate, we can determine what the price savings are.

Thank you all!

Brandon.

I'll say this, my BCM Standard midlength after I went from MOE HG and FSB to a shaved FSB and Troy VTAC Alpha rail, seemed much lighter swing weight, it makes the gun much more quicker and easier to shoot to have less weight up front. (In the context of a .223 rifle... as a disclaimer, my brother has a thin barreled, bolt action, .270 Winchester Savage, that about 3-4 shots and... I'm pretty much good)

Might be why so many people are jumping on the TAVOR bandwagon, it really talks to the fatigue side of things.

It seems that maybe weight location is more important (in this slight difference) than the weight itself to shooter fatigue.

Might be a good question for you and since Rob has some experience.

Have you guys noticed less fatigue with less weight in the front of the guns, are they easier to shoot/manipulate in your experience?

I think the theoretical application/implementation is as interesting as seeing the heat/accuracy/weight savings data.

Maybe give us impressions as in general if you can.

[rob_s]

Not sure I'm following your question, but you understand that a 6933 is identical to a 6720 but with 5" less barrel, right? I believe it's 18 vs 22 oz, stripped.

As to the "hidden" benefits of the lightweight, I've been meaning for years to do some testing in terms of target transitions, etc. but I just don't care enough to spend the time on that kind of thing anymore.

[BWT]

Not sure I'm following your question, but you understand that a 6933 is identical to a 6720 but with 5" less barrel, right? I believe it's 18 vs 22 oz, stripped.

As to the "hidden" benefits of the lightweight, I've been meaning for years to do some testing in terms of target transitions, etc. but I just don't care enough to spend the time on that kind of thing anymore.

Earlier when I posted this,


we can determine what the price savings are.

I meant


we can determine what the weight savings are.

That's understandable rob, I hate to say it. In this day and age, you have to prove a lot of things in the gun culture, because let's face it, people can be either A) Mistaken B) Exaggerating C) Straight out Lying or D) Ignorant. But, I respect the opinions of the people in this thread, I'd like to hear feed back. The more practical the feed back you can give, the better I think it'd serve the community.

Numbers are great, but numbers take time to record, shoot, test, re-test, and make sure it's tested fairly consistently among isolated variables. One of the things I'm excited about is getting a 12'' SBR because I feel like it'll be lighter and easier to transition. I don't know what to really expect with recoil, I can't imagine it's much worse.

I mean, it'd be great to have hard numbers but with ammo prices, time being the premium it is. I'm fine with impressions.

[Odin Bravo One]

They all "feel" the same to me. Could be I am not paying enough attention, I don't shoot them enough, or I honestly can't tell the difference between SBRs and 16" guns. Gun work, Gun good.

[BWT]

They all "feel" the same to me. Could be I am not paying enough attention, I don't shoot them enough, or I honestly can't tell the difference between SBRs and 16" guns. Gun work, Gun good.

You're also a Man's Man, which may disqualify your opinion. ;)

I'm actually only partially joking. Your physical conditioning may actually make the difference much less perceivable than a regular guy. I guess to get an appropriate gauge of the situation I'd need to find someone who struggled to handle a 6920. Either that or measure them with timers and accuracy to see if there was any perceivable difference in recoil, transition times, etc.

I do appreciate your input Sean. That does make the situation easier. I guess a question for you is have you ever noticed a real difference between the carbine 16" and SBRs as far as swing weights, etc.? Obviously there is a size benefit but what about weight specifically.

Thank you.

ETA: I re-read your reply, your answer was No you could not. Sorry I can't read well.

[Odin Bravo One]

I guess I just never looked at what was already a lightweight rifle/carbine as anything but lightweight.

Nope.......that was a lie.

In recruit training, our DI's had us hold our M16's by the FSA and a single finger, directly out in front of us, arm fully extended, at shoulder level. I seem to recall thinking that 8.79 lbs was a bitch of a weight to haul around like that for more than about 3 minutes.

I'm pretty sure I was over that idea by the time I was 18.5 years old, and those days were finally over.

I can absolutely tell when I pick it up if an AR is heavier than another. None of mine weigh in the same. But for what I see in the civilian oriented courses I teach (well, more like heard the cats so the real instructor doesn't have to is what I really do), and those courses I have attended as a student, I don't know that you could really quantify results. (That type of shooting I would describe as Close Quarters. Pretty much anything 100 and closer by my mind.) And I don't know that it would really matter under those types of conditions if a .000231 oz difference in a piece of gear we hang off of our rifle/carbine makes a tangible difference.

I learned the hard way that ounces lead to pounds, and unnecessary pounds lead to pain. Especially at 14,000' ASL. Or after swimming some un-Godly distance towing those Kittening pounds behind me, only to walk some other un-Godly distance some sadist thought up as a good arbitrary yardstick of performance. But we are not talking about ounces leading to pounds, and pounds leading to pain. We are only talking about ounces. Seriously. 1lb, 4 oz, is still only 20 ounces. I know people here routinely curl 20 ounces.......

I regress........

If my goal is to shoot a certain number of a certain type of drill with each carbine on the clock, and compare times.......I can do that. But if I nail the mount for my 25 yard brain shot first time, every time with an SBR (and my contention is that an SBR is easier/faster to "handle").........my average time will be distinctly faster overall than shooting the same COF with a 16" gun where my mount was less than perfect, even once. Thus proving with my data that I have evidence to support my claim of the SBR being faster to bring to bear. But how do I quantify that bobble in my mount? Well, scientists toss out shit all the time that doesn't support their claim, so if my claim were the opposite, I can simply do that to bring the times back to being comparable. Or include it, and prove my original theory that the shorter gun had a faster average time, and thereby is the "faster" to mount, or transition gun.

What about reloads, changing shooting positions, reacquiring the sight, etc.? That's an any given Sunday proposition for me and any of my ARs. I'll have days where I can run a MNQ @ 50 yards sub-15 seconds all day long, regardless of the length of the gun, optic, gear (ok, maybe I need the right gear.....i.e., MY gear), whatever. But I also have days that even with the shortest, and lightest of my AR's, it is all I can do to shoot that drill, keeping it under PAR, and the ensuring the accuracy requirement is met. I've watched TLG sub-5.0 clean the FAST enough times to be embarrassed that I can't manage to do two out of three to get a stinking coin. But I've also been present on the rare occasion where it has eluded him, even with the gun he has been carrying/training/practicing with, etc.

My point is, subjecting something like this to data collection is flawed in the conception, because there is one factor....... that "X" factor if you will, in the equation that is NOT equal each and every time we perform the task required to generate the data.........HUMAN PERFORMANCE. We never repeat the same exact sequence twice, exactly the same way. We practice and strive for perfection in repeatable performance, but that is what we are doing......practicing and training. We do that to minimize the max deviations to the execution of the skills that need to be performed repeatedly in order to achieve our desired end state. We engage ourselves in the pursuit of perfection, but is perfection my desired end state? That would be ideal, but it wouldn't be realistic. Personally, I dedicate myself to the pursuit of that perfection, with the desired end state to see improvement over time, and to enjoy the pursuit for the journey that it is, not simply the destination when I arrive. Someone much smarter than I am once said......"With one eye fixed on the destination, there is only one eye left with which to find the way".

I could spend an entire day on a range with a timer, photon plasma atom particle accelerator (just kidding, I don't have one of those), chrono, case of ammo, and lovely assistant to write down all of my results, but at the end of the day, the world won't end, a blackhole will not exist where the Earth once resided, the results will be all subjective, and I did nothing more than waste a perfectly good range session Kittening around when I could have been having actual fun, or (ugh, dare I say....) training.

I applaud and genuinely thank those who have that love of information, the attention to detail required, and the patience to go out and examine these types of things. I really do. It can provide some insight, IF taken in the proper context, and applied to the appropriate degree. But "data" it is not. Definitive it is not. The final answer it is not. And at the end of the day, when all is said and done............what it has to do with the price of tea in China, or whether or not I can effectively defend my home/family with my chosen configuration is only two things:

Jack and Kitten.

(And I'm not sure who yet.......but one of them is leaving town)

[Woodandsteel]

Any idea when the 6720 was introduced? I know that I bought two 6520s in 2005 or so and swapped one out for a flattop upper because the 6720 wasn't out at the time. I've been thinking of buying a 6720 just to put in the safe for a rainy day ever since they came out, but I can't remember when that was.

Not terribly important, just curious since many of us did the flattop conversion when there was no other choice.

Clyde Armory went to Colt and convinced them to create the AR6720, in response to all the requests for a 6520 with a flat-top conversion. They got the first 1000 units, (which was quite a big investment at that time) and had the exclusive for the first year after they brought it to market. The first guns were received in late March 2010, but weren't released for sale until April 2010.

Colt shipped the first 500 with removable carry handles, instead of the Matech rear sights they were supposed to have, so they were offered with a choice of either configuration.

The first 1000 came with the standard M4 stock, and were rollmarked "AR-15A4 Lightweight LE Carbine" on the left side and "RESTRICTED MILITARY/LAW ENFORCEMENT/GOVERNMENT/EXPORT USE ONLY" on the right side. Current models are rollmarked M4 Carbine and come with the Rogers Super Stock. For 2013 Colt recycled the AR-15A4 rollmark to use on their 20" barrelled semiauto version of the M16A4.

Full disclosure: I work for Clyde Armory, but I was not there in 2010 and had no part in the release of the 6720. It's a cool rifle, and I'm a fan of lightweight barrels.

[LSP972]

I applaud and genuinely thank those who have that love of information, the attention to detail required, and the patience to go out and examine these types of things. I really do. It can provide some insight, IF taken in the proper context, and applied to the appropriate degree. But "data" it is not.

WELL stated. Bravo, sir.

.

[LSP972]

To further muddy the "lineage" waters...

I was dragged into Wally World Saturday by the wife, and naturally went to the sporting goods section to see what I could see. Lo and behold, there was a Colt carbine for a REAL good price... but of a configuration I didn't recognize.

Standard civilian upper with the current oval handguards, regular FSB, stepped barrel & Pic rail; MagPul rear sight; Rogers Super Stoc (which I had never heard of prior to this), and "Colt Defense" and "M4" markings on the lower. The clerk kept referring to it as a 6920 (since that was what was written on the string tag), and I kept asking him where the removeable carrying handle was.

Rather than continue to argue with him, I asked him to get the box. The label said "6920 (2013 Configuration)". The serial # matched to the carbine, so....

WTF???

Anyway, I bought it, and when I got home I checked Colt's site and didn't find this particular example. So I can only surmise its something relatively new.

Don't care. Its a Colt, and the price was right. I plan to leave it bone stock, no light or optic. We have a 6520 and a 6720 with H-1s and white lights; this one will be a spare.

I dunno, if I run across a killer deal on an H-1 with riser mount I may scarf it. Also, I now remember I have a NIB InSight MRDS gathering dust that might do if I got a mount.

Anyone, off the top of their head, have a suggestion for a suitable mount for that puppy?

.

[rob_s]

But "data" it is not.

What, then, do you think data is?

[BWT]

What, then, do you think data is?

I think what he's saying is humans aren't 100% consistent.

Therefore real data is hard to quantify. A 300 lb man will have a different experience of target transitions than a 135 lb teenager.

Also no one here could duplicate the same times (literally) on a drill back to back with the same exact shot placements and then pick up a lighter weight gun and then somehow run mildly (hypothetically) faster transitions with the same exact times and form.

Meaning you couldn't shoot like an exactly triple tap to an A Zone with a 2.3" spread and transition to another target 5 meters apart and do the same size group in the same amount of time, on demand.

He's saying its mostly unmeasurable.

I'd be inclined to agree. Really what you'd need is a machine that used the same amount of ft-lbs of torque and same exact influences on both guns to gather the information to measure time saved or lost by interference.

I'd say the best we can reasonably get from people is impressions. I used to read a lot at NFATalk.org about Suppressor meterings and even shot with them at one outing.

Even then atmospheric pressure, temperature (air density), and the environment (shooting in an open field or some place sound might reflect) had a huge affect on that, that's why they shot certain guns/ silencers at every shoot to establish a baseline.

Sean is spot on, real testing? Like REAL testing is boring.

ETA: I mean you could test the same gun, same place, suppressor, ammo, etc. the same place at different times of day and see a difference in sound reduction levels.

So. I think that's what he's alluding to.

[Woodandsteel]

To further muddy the "lineage" waters...

I was dragged into Wally World Saturday by the wife, and naturally went to the sporting goods section to see what I could see. Lo and behold, there was a Colt carbine for a REAL good price... but of a configuration I didn't recognize.

Standard civilian upper with the current oval handguards, regular FSB, stepped barrel & Pic rail; MagPul rear sight; Rogers Super Stoc (which I had never heard of prior to this), and "Colt Defense" and "M4" markings on the lower. The clerk kept referring to it as a 6920 (since that was what was written on the string tag), and I kept asking him where the removeable carrying handle was.

Rather than continue to argue with him, I asked him to get the box. The label said "6920 (2013 Configuration)". The serial # matched to the carbine, so....

WTF???

Anyway, I bought it, and when I got home I checked Colt's site and didn't find this particular example. So I can only surmise its something relatively new.

Don't care. Its a Colt, and the price was right. I plan to leave it bone stock, no light or optic. We have a 6520 and a 6720 with H-1s and white lights; this one will be a spare.

I dunno, if I run across a killer deal on an H-1 with riser mount I may scarf it. Also, I now remember I have a NIB InSight MRDS gathering dust that might do if I got a mount.

Anyone, off the top of their head, have a suggestion for a suitable mount for that puppy?

.

The gun is exactly what the label says: LE6920 (2013 Configuration).

For 2013 Colt dropped the carry handles from all their guns. The 6920 an 6720 now come with a Magpul rear sight and Rogers Super Stock. Most guns come with one mag and no longer include the sling or cleaning kit.

[Jay Cunningham]

Mine came with two 20 round PMAGs and the cleaning rod with brushes.

Ditching the carry handle makes sense.

[Odin Bravo One]

What, then, do you think data is?

Main Entry: da·ta
Pronunciation: \ˈdā-tə, ˈda- also ˈdä-\
Function: noun plural but singular or plural in construction
Usage: often attributive
Etymology: Latin, plural of datum
Date: 1646
1 : factual information (as measurements or statistics) used as a basis for reasoning, discussion, or calculation <the data is plentiful and easily available — H. A. Gleason, Jr.

Certainly the information recorded in the examples of using a timer and a determined set of drills is "factual" in the sense that unless I lied in my recording of the information it is a fact that those were the results. But the results of such tests will not be "factual".

We can certainly use it for the purpose of discussion, but it is discussion simply for the purpose of discussion, as no concrete "facts" will be a result of said discussion. Such a discussion also has zero relevance in the application of such a carbine in a lethal force encounter.

[LSP972]

The gun is exactly what the label says: LE6920 (2013 Configuration).

For 2013 Colt dropped the carry handles from all their guns. The 6920 an 6720 now come with a Magpul rear sight and Rogers Super Stock. Most guns come with one mag and no longer include the sling or cleaning kit.

Ah, so. Yup, one 30 round plastic magazine, no sling or cleaning kit.

Thanks for the info.

.

[Woodandsteel]

Mine came with two 20 round PMAGs and the cleaning rod with brushes.

Ditching the carry handle makes sense.

If I remember correctly, I believe the 6720 was the first Colt to come standard with Magpul PMAGs.

[LSP972]

Now that I think about it, my 6720 came with a pair of 20 round Pmags as well.

.

[Guinnessman]

The 6720 that I bought last summer came with a Matech BUIS and the 20 round PMAG's as well. I was actually a little upset to see Colt switch from two Aluminum Colt 20 round mags to the PMAG's. I love the Colt 20 rounders and would really like to buy some more.

All of my 20 round Pmags have functioned just fine. I just prefer aluminum mags.

[Chuck Haggard]

I literally have a potato sack of Colt 20 round mags. Picked many of them up while on foot on FT. Riley while doing field problems or land nav, a bunch were thrown out by my unit when we got 30 round mags in stock in the armory. I went dumpster diving...

I actually greatly prefer the quality 30 round mags, but the old Colt 20 rounders with the aluminum followers always seemed to work reliably.

[Molon]

I'll be interested to see some groups from the 6720 with a scope mounted.


While the Colt 16” light-weight “pencil” barrels found on the Colt 6520 and 6720 variants are not quite as accurate the Colt 16” government-profile barrels, they are certainly accurate enough for their intended role on a duty/self-defense carbine. What you will see with the light-weight barrels, is a greater degree of variability in the extreme spread from shot-group to shot-group. Because of this, I prefer to use a larger sample size of shot-groups when evaluating the accuracy of these light-weight barrels in order to obtain a better representation of their probable accuracy. While I normally use three 10-shot groups fired from 100 yards in an accuracy evaluation, I like to use six 10-shot groups from the same distance for the light-weight barrels.

Most of you are probably aware that the Colt light-weight barrels have the same profile under the hand-guards as Colt’s government profile barrels. The government profile barrels are heavier from the gas-block/front-sight-base journal forward to the muzzle. A stripped Colt 16” light-weight barrel will have a weight of approximately 1 pound 6 ounces, while a stripped Colt 16” government-profile barrel (with the M203 cut-out) will weigh of approximately 1 pound 12 ounces. (A stripped Colt 16” HBAR will have a weight of approximately 2 pounds 3 ounces.)



Colt 6520/6720, 16" light-weight barrel: 1 pound, 6 ounces.
http://www.box.net/shared/static/x7ykufvv3j.jpg



Colt 6920, 16" M4/governmnet profile barrel: 1 pound, 12 ounces.
http://www.box.net/shared/static/qhjpk4qlr3.jpg


Colt 6721, 16" HBAR: 2 pounds, 3.4 ounces.
http://www.box.net/shared/static/3bnl8bdr23.jpg




The gas-block/front-sight-journal of the light-weight barrel has a diameter of 0.625” compared to a diameter of 0.750” for the government profile barrel. The light-weight barrel profile has a slight taper underneath the handguards from the chamber to the gas block with an average diameter of approximately 0.64”. The light-weight barrel is chrome lined, has a NATO chamber and a 1:7” twist. This barrel employs a carbine gas system and has M4 feedramps.

I conducted an accuracy (technically precision) evaluation of a 16” Colt light-weight barrel from a distance of 100 yards with the results shown below. This accuracy evaluation was performed with a LaRue Tactical free-float handguard installed.


The test vehicle.

http://www.box.net/shared/static/b3lq26fcpa.jpg



Shooting was conducted from a concrete bench-rest using a Sinclair Windage Bench Rest in front and a Protektor bunny-ear bag under the stock. Sighting was performed using a Leupold VAR-X III with a mirage shade. Magnification was set at 25X and the scope was adjusted to be parallax free at 100 yards. Wind conditions were monitored using a Wind probe. The ammunition used for this evaluation was one of my standardized match-grade hand-loads topped with Sierra 55 grain BlitzKings. When fired from a 20” Colt M16A2 barrel this load has a nominal muzzle velocity of 3000 FPS. This particular hand-load has grouped extremely well in every AR-15 barrel that I have tested with it. When fired from one of my precision AR-15s with a 24” stainless-steel Krieger heavy- barrel, this load has turned in ½ MOA 10-shot groups at 100 yards.


https://app.box.com/shared/static/c3nj830tjxcph7zq8vm7.jpg


The Wind Probe.

https://app.box.com/shared/static/lkg47ptc04.jpg



Six 10-shot groups were fired in a row in a slow and steady manner. Those groups had the following extreme spreads:

Group #1 . . . ES=1.18”
Group #2 . . . ES=1.92”
Group #3 . . . ES=1.28”
Group #4 . . . ES=2.53”
Group #5 . . . ES=0.96”
Group #6 . . . ES=2.24”

The average extreme spread for all six of the 10-shot groups is 1.69”. Using RSI Shooting Lab, I over-layed all six groups on each other to form a 60-shot composite group. The composite group had a mean radius of 0.56”.


http://www.box.net/shared/static/z63cvxm04g.jpg


The smallest 10-shot group.


http://www.box.net/shared/static/pny6ravij6.jpg


The largest 10-shot group.

http://www.box.net/shared/static/mikliee7f7.jpg


For a comparison, I fired three 10-shot groups at 100 yards from a free-floated Colt 16” M4/government profile barrel (6920), a free-floated Colt 16” HBAR (6721) and a second 16” Colt light-weight barrel (6520/6720). The three 10-shot groups from each of these barrels were over-layed on each other respectively using RSI Shooting Lab to form 30-shot composite groups. The results are shown below.



https://app.box.com/shared/static/in8cal2pcg.jpg



For those of you that might not be familiar with the mean radius method of measuring the radial dispersion of shot groups, I'll be adding an explanation in a follow-on post. As a rule of thumb, the extreme spread will be approximately three times larger than the mean radius.



....

[Molon]

I suspect that the RDS is probably the limiting factor with regards to accuracy.


Yes, but probably not by a lot. As I demonstrated in my previous post, the Colt 16” light-weight barrel produced an average extreme spread of approximately 1.7 MOA for 10-shot groups at 100 yards when using a high-magnification scope. Previous testing has shown that an Aimpoint RDS with a 4 MOA dot limits my precision to approximately 1.25 MOA for 10-shot groups at 100 yards.


Precision Shooting With an Aimpoint


First and foremost, the Aimpoint red dot sight is a combat sight. Its primary purpose is for use in situations that require “reflexive shooting” at multiple targets, at close ranges. The Aimpoint excels in this type of shooting because it easily allows you to shoot with both eyes open and to focus on the target while shooting. All of my self-defense AR-15s have Aimpoints mounted on them. However, should the need arise (for example, making a head-shot on an aggressor at 100 yards who has most of his body behind hard cover) the Aimpoint sight is certainly up to the task of making precision shots.


There are those who claim that when using an Aimpoint sight with a four minute of angle dot, that it is not possible to shoot groups that are smaller than four minutes of angle in extreme spread. One such person has gone so far as to claim that groups shot from 100 yards using an Aimpoint with a 4 MOA dot will be “greater than 4 inches. Usually much greater.” As we shall soon see, such statements are completely false.


To determine the level of precision obtainable when using an Aimpoint sight with a 4 MOA dot, I mounted an Aimpoint ML2 with a 4 MOA dot on one of my Krieger barreled AR-15s. This AR-15 is easily capable of producing consistent sub-MOA 10-shot groups at 100 yards when using a high magnification scope. Shooting with the Aimpoint sight was done from a bench-rest at a distance of 100 yards using NRA 200 yard High Power type targets that I scaled-down for 100 yards. (The aiming black is approximately the same width as a human head.) Sighting was done using the whole dot centered on the bullseye. Three 10-shot groups were fired in a row for evaluation.





http://www.box.net/shared/static/q9l5quki4y.jpg



http://www.box.net/shared/static/qmpuquyrp1.jpg




Zeroing the Aimpoint sight at 100 yards was conducted during a down-pour with 20-25 mph winds. The first two 10-shot groups were also fired under these conditions. The first 10-shot group had an extreme spread of 1.41”.




http://www.box.net/shared/static/m97mctqy35.jpg



With another couple clicks of windage and elevation adjustment, the second 10-shot group had all shots going into the X-ring. The extreme spread for this group was 1.19”.




http://www.box.net/shared/static/sd5xfhre13.jpg




Just as quickly as the down-pour had started, the rain stopped, the winds died down and the sun began shining again. I posted a new and dry target on the 100 yard backer and continued shooting. The third 10-shot group had an extreme spread of 1.14”. The average extreme spread for all three of the 10-shot groups was 1.25”.





http://www.box.net/shared/static/vcm40jjrx5.jpg




….

[Molon]

The Mean Radius

Mean radius is the method of measurement of the dispersion of shot-groups used by the US Military for accuracy testing of ammunition. It provides a more useful analysis of the consistency of ammunition and rifle accuracy.

The typical method used to measure a group consists of measuring the distance between the centers of the two most outlying shots of a group. This would be the “extreme spread” of the group. We are essentially measuring the distance between the two worst shots of a group. Take a look at the two targets below.

https://www.box.com/shared/static/05kmhft6cvk0w96q771e.jpg

Most people would intuitively conclude that the second target shown is the “better” group. Measuring the two groups using the extreme spread method, we find that both groups measure 2.1”. Once again with the typical method of measuring groups we are measuring the distance between the two worst shots of the group. This method tells us nothing about the other eight shots in the group. So how can we quantitatively show that the second group is better than the first? (Yes, we could score the groups using “X-ring” count, but this does not give us any differential information about all those shots in the X-ring.) This is were the mean radius method comes in. It will give us that extra information we need to better analyze our groups, rifles and ammuntion. If I just reported the measurements of the two groups above using the extreme spread meathod, without a picture, you would assume that the two groups were very much the same. Using the mean radius method shows that the second group is much more consistent. It has a mean radius of 0.43” compared to 0.78” for the first group.

Mean radius as defined in Hatcher's Notebook “is the average distance of all the shots from the center of the group. It is usually about one third the group diameter (extreme spread).”

To obtain the mean radius of a shot group, measure the heights of all shots above an arbitrarily chosen horizontal line. Average these measurements. The result is the height of the center of the group above the chosen line. Then in the same way get the horizontal distance of the center from some vertical line, such as for instance, the left edge of the target. These two measurements will locate the group center.

Now measure the distance of each shot from this center. The average of these measures is the mean radius.

Once you get the hang of measuring groups using the mean radius it becomes very simple to do. While being very simple to do, it is also very time consuming. Modern software programs such as RSI Shooting Lab make determining the mean radius a snap.

The picture below is a screen snapshot from RSI Shooting Lab. The red cross is the center of the group (a little high and right of the aiming point). The long red line shows the two shots forming the extreme spread or group size. The yellow line from the red cross to one of the shots is a radius. Measure all the radii and take the average to obtain the mean radius.

https://www.box.com/shared/static/e5h310mx2lw65cuuwrfk.jpg

[Molon]

Mean Radius Demonstration

Let’s say you fired a 5-shot group from 100 yards and the resulting target looks like this. (The X-ring measures 1.5” and the 10-ring measures 3.5”.)

https://www.box.com/shared/static/pn6jf1qeuywk5a42jzcz.jpg

The extreme spread of the group measures 2.83”, but we want to find the mean radius (or average group radius.) In order to find the mean radius we must first find the center of the group. By “eye-balling” the target most people would see that the group is centered to the left of the “X-ring” and probably a little high, but we need to find the exact location of the center of the group.

Locating the Center of the Group

The first step in finding the center of the group is to find the lowest shot of the group and draw a horizontal line through the center of that shot.

https://www.box.com/shared/static/hg77du60v6jwj6qnhsd2.jpg

Next, find the left-most shot of the group and draw a vertical line through the center of that shot.

https://www.box.com/shared/static/qyqecvzn8slmls96199f.jpg

Now measure the distance from the horizontal line to the other four shots of the group that are above that line. Add those numbers together and divide by the total number of shots in the group (5).

https://www.box.com/shared/static/k0uuxzzb1weo3ppgluz7.jpg

2.50” + 1.03” + 2.01” + 1.30” = 6.84”

Divide by 5 to get 1.37”. This number is the elevation component of the center of the group.

Next we need to find the windage component of the center of the group. From the vertical line, measure the distance to the other four shots of the group that are to the right of the line. Add those numbers together and again divide by the total number of shots in the group (5).

https://www.box.com/shared/static/ncg6hkbmcv1kyyvtdua1.jpg

1.76” + 2.54” + 0.45” + 1.19” = 5.94”

Divide by 5 to get 1.19” This is the windage component of the center of the group.

Finding the windage and elevation components of the center of the group is the most difficult part of this process. Once that is done the rest of the process is a piece of cake.

Using the windage and elevation components, locate the position on the target that is 1.37” (elevation component) above the horizontal line and 1.19” (windage component) to the right of the vertical line. This location is the center of the group!

https://www.box.com/shared/static/46cr6kei23k2npjbwopy.jpg


Determining the Mean Radius

Now that we have located the position of the center of the group, the first step in determining the mean radius is to measure the distance from the center of the group to the center of one of the shots. This line is a single “radius”.

https://www.box.com/shared/static/vm7k0jzt5h941pfldlhj.jpg


Now measure the distance from the center of the group to the center of each of the rest of the shots in the group. Add the measurements of all the radii together and then divide by the total number of shots in the group (5).

https://www.box.com/shared/static/lv461k9kjilx3jndshs4.jpg

0.85” + 1.35” + 1.38” + 0.84” + 1.61” = 6.03”

Divide by 5 to get 1.21”. This is the mean radius (or average group radius) of the group!

Using the mean radius measurement to scribe a circle around the center of the group gives you a graphic representation of the mean radius. This shows the average accuracy of all the shots in the group. This demonstrates why the mean radius is much more useful than the extreme spread in evaluating the accuracy of our rifles and ammunition.

https://www.box.com/shared/static/g1480t5ca47zrae1du8i.jpg



The table below will give you an idea of the relationship between the mean radius and extreme spread.

http://www.box.net/shared/static/e4ckmi2y36.jpg



....

[littlejerry]

Mean Radius Demonstration

Let’s say you fired a 5-shot group from 100 yards and the resulting target looks like this. (The X-ring measures 1.5” and the 10-ring measures 3.5”.)

https://www.box.com/shared/static/pn6jf1qeuywk5a42jzcz.jpg

The extreme spread of the group measures 2.83”, but we want to find the mean radius (or average group radius.) In order to find the mean radius we must first find the center of the group. By “eye-balling” the target most people would see that the group is centered to the left of the “X-ring” and probably a little high, but we need to find the exact location of the center of the group.

Locating the Center of the Group

The first step in finding the center of the group is to find the lowest shot of the group and draw a horizontal line through the center of that shot.

https://www.box.com/shared/static/hg77du60v6jwj6qnhsd2.jpg

Next, find the left-most shot of the group and draw a vertical line through the center of that shot.

https://www.box.com/shared/static/qyqecvzn8slmls96199f.jpg

Now measure the distance from the horizontal line to the other four shots of the group that are above that line. Add those numbers together and divide by the total number of shots in the group (5).

https://www.box.com/shared/static/k0uuxzzb1weo3ppgluz7.jpg

2.50” + 1.03” + 2.01” + 1.30” = 6.84”

Divide by 5 to get 1.37”. This number is the elevation component of the center of the group.

Next we need to find the windage component of the center of the group. From the vertical line, measure the distance to the other four shots of the group that are to the right of the line. Add those numbers together and again divide by the total number of shots in the group (5).

https://www.box.com/shared/static/ncg6hkbmcv1kyyvtdua1.jpg

1.76” + 2.54” + 0.45” + 1.19” = 5.94”

Divide by 5 to get 1.19” This is the windage component of the center of the group.

Finding the windage and elevation components of the center of the group is the most difficult part of this process. Once that is done the rest of the process is a piece of cake.

Using the windage and elevation components, locate the position on the target that is 1.37” (elevation component) above the horizontal line and 1.19” (windage component) to the right of the vertical line. This location is the center of the group!

https://www.box.com/shared/static/46cr6kei23k2npjbwopy.jpg


Determining the Mean Radius

Now that we have located the position of the center of the group, the first step in determining the mean radius is to measure the distance from the center of the group to the center of one of the shots. This line is a single “radius”.

https://www.box.com/shared/static/vm7k0jzt5h941pfldlhj.jpg


Now measure the distance from the center of the group to the center of each of the rest of the shots in the group. Add the measurements of all the radii together and then divide by the total number of shots in the group (5).

https://www.box.com/shared/static/lv461k9kjilx3jndshs4.jpg

0.85” + 1.35” + 1.38” + 0.84” + 1.61” = 6.03”

Divide by 5 to get 1.21”. This is the mean radius (or average group radius) of the group!

Using the mean radius measurement to scribe a circle around the center of the group gives you a graphic representation of the mean radius. This shows the average accuracy of all the shots in the group. This demonstrates why the mean radius is much more useful than the extreme spread in evaluating the accuracy of our rifles and ammunition.

https://www.box.com/shared/static/g1480t5ca47zrae1du8i.jpg



The table below will give you an idea of the relationship between the mean radius and extreme spread.

http://www.box.net/shared/static/e4ckmi2y36.jpg



....
Molon, great info! I remember seeing it posted on ARFCOM some time ago.

Its great to see you active again. I always enjoyed reading your evaluations. You are a true asset to the community.

[Savage Hands]

Molon, great info! I remember seeing it posted on ARFCOM some time ago.

Its great to see you active again. I always enjoyed reading your evaluations. You are a true asset to the community.



I agree!

[LittleLebowski]

Molon, great info! I remember seeing it posted on ARFCOM some time ago.

Its great to see you active again. I always enjoyed reading your evaluations. You are a true asset to the community.

Agreed. Welcome, Molon!

[Al T.]

Its great to see you active again. I always enjoyed reading your evaluations. You are a true asset to the community.

Ditto. Great to have you here. :)

[Colt191145lover]

Welcome Molon ! Its great to see your posts again!!!

[Clyde from Carolina]

Fascinating thread. I have my eyes on a 6721 for a good price and this made for very interesting reading.

[Molon]

Here are some pics of some of my builds using the 16" Colt light-weight (6520/6720) barrel.



https://app.box.com/shared/static/1xeqpm24crajjpfwr4nj.jpg



https://app.box.com/shared/static/tomx48tqynmjmq80igpy.jpg



https://app.box.com/shared/static/05rcv7pk3obhe111wzvr.jpg



https://app.box.com/shared/static/4p4h2q4aq15cnz39mcqx.jpg



....

[Failure2Stop]

Molon, good to see you again man.


Typos brought to you via Tapatalk and autocorrect.

[DacoRoman]

Hello Gents.

I just put a RIS II rail on a 6720. Reasons: get a good forward hand grip and place a pistol light directly to the rail (I prefer 3 o clock). I have an Aimpoint Pro, but I'm thinking of a 1-4 or 1-6x variable. Necessities are that it be daylight visible and a decent reticle to allow close quarter to 400 yards or so. For example I've been looking at the vortex razor gen II 1-6x, but is this too much scope for this type of gun? Also would I negate the whole LW idea with a scope that is pretty heavy? What would be a good low power variable match up with the 6720 in your opinions? Or would a 3x acog or some such be better suited. I can use the RDS out to 300, yes, but I want a variable for more potential precision especially on smaller partially obscured targets if necessary.

[DocGKR]

For a LW AR15, a small RDS with 3x magnifier on a LT 649 swing mount is a great way to go. For a low power variable, something like a 1-4x or 1-6x by a good vendor like Trij, NF, Leup, S&B, or even a Bushnell or Vortex would work. I try to avoid the fixed power ACOG's these days.

[TheTrevor]

I've been exceptionally pleased with the Burris MTAC 1-4X. I don't like the mount which stacks a red dot atop the scope, but I love running it with 45-degree offset iron sights or red dot. It's "only" a 4X scope but it's good to 300+ yards in my experience. Oh, and the holdover reticle works very well.

[DacoRoman]

Thanks for the replies. I didn't want to be a dork and put too much scope on a rifle with a LW barrel. I just noticed that there is a LW carbine thread and I'll post a f/u question there regarding this "too much scope" for a LW carbine idea, which in a sense has already been addressed by the Doc.

[Jay Cunningham]

I think 1.1x - 6x isn't too much scope for a rifle like this. Beyond that it may be.

[TGS]

Define the purpose of said LW rifle, and it may still be appropriate to have even a 3-12x.

If it's a LW AR15 built for varmint hunting where you'll only be shooting 1-3 shots, then it's wholly appropriate....and there's plenty of reasons to choose a LW AR15 over a bolt-action for that role.

[DacoRoman]

Thanks for the comments. I'm close to deciding which variable I'll be getting. Here are a couple of pictures. The way I ran it in a class last year, and now with a RIS II rail on it.
I'm the one with the white hat
http://i1116.photobucket.com/albums/k572/BCristianJ/redbackoneclass15_zpsa921eaf5.jpg
http://i1116.photobucket.com/albums/k572/BCristianJ/6720RISII_zps0bb6f832.jpg

[DacoRoman]

Define the purpose of said LW rifle, and it may still be appropriate to have even a 3-12x.

If it's a LW AR15 built for varmint hunting where you'll only be shooting 1-3 shots, then it's wholly appropriate....and there's plenty of reasons to choose a LW AR15 over a bolt-action for that role.


Homestead defense rifle, planning on going to a range where I could shoot steel out to 400-500 yards. I would love to go back and do the CSAT course where I was shooting out to 350 yards with irons (6920) but this time with a variable, since I didn't get a single hit; focusing on the front sight made me completely loose the target. But even a RDS would have helped me out I think.

[Kyle Reese]

I like your setup in both pics. No frills, no BS.

:)

[LittleLebowski]

I like seeing other folks that don't obsess over color matching :D

[littlejerry]

I like seeing other folks that don't obsess over color matching :D

Dude, you can't be tier 1 if your FDE stock doesn't match your coyote pistol grip.

And coyote is so 2008. All the current operators have discovered urban grey

[John Hearne]

And coyote is so 2008. All the current operators have discovered urban grey

Did you say urban gay?

[DacoRoman]

I like seeing other folks that don't obsess over color matching :D

That's hilarious guys! Actually, it is very funny you mention that because even my wife said: "you don't match at all, why don't you at least wear a different colored hat!", although I know you are probably talking about my rifle :D. I guess I don't have a MetroTactical bone in my body…and it translated over into my laissez faire attitude regarding the color palette of my rifle..although the fact that I used both "laissez faire" and "color palette" may mean I'm a little urban ghey.

[TheTrevor]

Did you say urban gay?

Was that really necessary?

[DacoRoman]

I like your setup in both pics. No frills, no BS.

:)
Thank you. I did catch flak from a friend for keeping the lowly MaTech and not going with the latest trendy rail..but I don't want to be someone that treats his AR's like barbie dolls constantly changing stuff around like some people I know..I just think it's useless unless there is a specific need

[DacoRoman]

Someone just asked me and i don't know the answer to: is port erosion more likely in a LW barrel? Would CHF'ing ameliorate this?

[Kyle Reese]

Thank you. I did catch flak from a friend for keeping the lowly MaTech and not going with the latest trendy rail..but I don't want to be someone that treats his AR's like barbie dolls constantly changing stuff around like some people I know..I just think it's useless unless there is a specific need

Good on ya. You're ahead of the power curve because you're training with your carbine, and not just slapping the latest kit on it and admiring it in your safe. As a BUIS, the Matech is certainly a serviceable option as a back up to your optic.

[Jay Cunningham]

I think my AR6720 may be a great candidate for the new MOE SL furniture.


http://store.magpul.com/images/uploads/266_1404_popup.jpg


http://store.magpul.com/images/uploads/263_1465_popup.jpg


http://store.magpul.com/images/uploads/265_1407_popup.jpg

[rob_s]

That's a good idea.

I've been mulling over the various shortcomings of the 6720 relative to recommending them to new shooters who want to get out immediately and start competing or training with it, or both. The main shortcomings I came up with were
1) lack of good sling attachment point front
2) lack of good sling attachment point rear
3) lack of good light-mounting option
4) restricted forward hand placement

The independent solutions I arrived at were
1) MI FSB light mount with QD socket
2) MI M4 stock QD attachment
3) see #1
4) I really got nothing

That MOE furniture would address a lot of the issues. The forend is supposed to be MLOK, right?

[Jay Cunningham]

That MOE furniture would address a lot of the issues. The forend is supposed to be MLOK, right?

Yes, and while limited in selection now it would seem that MagPul is going all-in with it.

[Kyle Reese]

Yup. Throw on a two-point sling, WML and an Aimpoint PRO and you've got a winner.

[Jay Cunningham]

I'm think I'm heading in that direction. I may MagPul this thing all up over a period of time... might as well give some of their newer stuff a fair shake. I think they redesigned their sling, so I wouldn't mind trying it.

[rob_s]

Yup. Throw on a two-point sling, WML and an Aimpoint PRO and you've got a winner.
I bought a PRO pretty much just because I saw 6720s down to $800 and I wanted to play with the idea of a first-timer gun.


I'm think I'm heading in that direction. I may MagPul this thing all up over a period of time... might as well give some of their newer stuff a fair shake. I think they redesigned their sling, so I wouldn't mind trying it.
I'm playing with one of their new slings. I think I'm trying to do too much with it, as I was testing using it in all four attachment points. Attaching it to the stock with the 2-to-1-point tail on it is annoying as the metal socket portion gets in the way. I'm going to try taking that off and see if it improves. Otherwise it seems good.

[breakingtime91]

The proctor sling from way of the gun gets rid of the need for sling attachment points. Seems like a good alternative. Any links to cheap 6920s or 6720s would be awesome guys, going back to the AR after a year with the AK.

[Jay Cunningham]

Damn.

[Kyle Reese]

If you've got the coin, buy one and stick it in the safe.

[rob_s]

The proctor sling from way of the gun gets rid of the need for sling attachment points. Seems like a good alternative.

Oh sure, and there are others as well, but I'm not a fan of the way that any of them attach. And, I'd rather recommend a new shooter a way to attach a variety of slings that he might want to try rather than stick him with what I already consider to be an unacceptable attachment method.

[breakingtime91]

Any reason why you don't like the para-cord attachment method? Also if its because you think it will break I would appreciate evidence or an example of a scenario. I have been researching this sling for awhile now and have a few doubts still but Frank Proctor seems like a good guy and good to go.

[LHS]

Sample size of one, but interesting nonetheless:

A buddy of mine just got one of the 6720s from PSA, and while the carrier key was staked properly, the castle nut wasn't staked at all. Easy to fix, but not something I expected to find on a Colt.

[Jay Cunningham]

Sample size of one, but interesting nonetheless:

A buddy of mine just got one of the 6720s from PSA, and while the carrier key was staked properly, the castle nut wasn't staked at all. Easy to fix, but not something I expected to find on a Colt.

That's disappointing. However it wouldn't surprise me to see a QC slip from Colt in light of all these variants they're currently putting together. I don't have evidence for that, just saying I can see it happen.

[breakingtime91]

is their a reliable piece/method of picattany (spelling?) installation on top of the original m4 hand-guard that comes with the 6720? Try to mount my thorn tail offset and surefire g2 to it.

[Jay Cunningham]

is their a reliable piece/method of picattany (spelling?) installation on top of the original m4 hand-guard that comes with the 6720? Try to mount my thorn tail offset and surefire g2 to it.

Impact Weapon Components will have what you need.

[breakingtime91]

Jay can you show me some pictures of what I need to check when I get my colt (like what lhs was talking about) and how to make sure its good to go?

[Jay Cunningham]

Jay can you show me some pictures of what I need to check when I get my colt (like what lhs was talking about) and how to make sure its good to go?

Damn I wished you lived closer, tomorrow I'm teaching a half day AR-15 Technical Inspection Cinic just outside of Pittsburgh, PA.

[breakingtime91]

damn. Think I should still order one of these colt from PSA? srry for the questions but LHS has me questioning it now

[Jay Cunningham]

For the money?

My God yes.

[breakingtime91]

Thanks jay, still cant find that picattany section on impact site. I'm failing at the internet today.

[Jay Cunningham]

Go back and look at this post and check out the pic:

http://pistol-forum.com/showthread.php?8593-Thoughts-on-the-Colt-AR6720-Lightweight-LE-Carbine&p=141419&viewfull=1#post141419

You don't need a pic rail, you can directly attach to the M4 handguards.


eta: http://www.impactweaponscomponents.com/product/tmc-1-light-mount-n-slot/

[rob_s]

Any reason why you don't like the para-cord attachment method? Also if its because you think it will break I would appreciate evidence or an example of a scenario. I have been researching this sling for awhile now and have a few doubts still but Frank Proctor seems like a good guy and good to go.

As I said, when making suggestions for new shooters I'd prefer them to have the flexibility that QD affords to try other options.

I've tied on slings before, there's nothing new in that, and my negative experience with same trumps anyone else's go-to-go-ness. For my own guns it's rotation-limited, QD-socket-mounted slings only.

[TR675]

Go back and look at this post and check out the pic:

http://pistol-forum.com/showthread.php?8593-Thoughts-on-the-Colt-AR6720-Lightweight-LE-Carbine&p=141419&viewfull=1#post141419

You don't need a pic rail, you can directly attach to the M4 handguards.


eta: http://www.impactweaponscomponents.com/product/tmc-1-light-mount-n-slot/

Jay, this only works for single-heat shielded forearms (without modifying them, anyway), right? IIRC my 2007 vintage Colt's handguards had double heat shields and something like this wouldn't have worked.

[Jay Cunningham]

My pictured gun is wearing an M4 handguard. I removed the heat shields, then reinstalled them.

[LittleLebowski]

damn. Think I should still order one of these colt from PSA? srry for the questions but LHS has me questioning it now

Grab it.

[breakingtime91]

I already own the thorntail offset, so I was trying to utilize it.

[breakingtime91]

Grab it.

waiting on my ffl to get back to me right now.. becoming irritated lol

[3-7-77]

I order one from PSA a couple weeks back. Their shipping was actually quite quick.

[breakingtime91]

Just ordered mine. 809 with shipping. Now any recommendations on rails for the front would be sweet :cool:

[Jay Cunningham]

You could try that new MagPul SL fore end and the cantilever M LOK we were talking about...

[breakingtime91]

Did we ever include if free float is worth the extra $ (also I'm looking at the Magpul SL)

[Jay Cunningham]

Gawd, that's a whole separate discussion.

[breakingtime91]

Gawd, that's a whole separate discussion.

Come on jay, help a brother out :cool:

[Sadmin]

I used the c4 cutout- it's great but really alters the reasoning for getting a deal on the rifle itself. I just ordered a BA Tribute m4 upper to play with, the Magpul SL handguard looks like the ticket.


Sent from my iPhone using Tapatalk

[tremiles]

I have no personal experience with it, but MI's M-Lok fore-end looks pretty light and has QD mounts built in if you're dead set on a FF rail. Shave your FSB, and you could have a relatively LW rifle with an inexpensive rail.

[BWT]

Did we ever include if free float is worth the extra $ (also I'm looking at the Magpul SL)

How accurate are you expecting the gun to be and how will you be shooting it?

I'd say get the gun, an RDS, zero, and shoot it.

The new handguards give more reach; which may be all you'd need.

ETA: I'd really endorse using the gun first close to stock, different handguards aren't a big deal.

I put a 13" VTAC alpha rail on my Midlength; with the cost to shave the FSB, the rail, and a new fixed FSB to mount on that said rail?

If I had to ball park $320-350?

You could buy 20 quality magazines and 420-ish rounds of 5.56 M855 for that.

http://palmettostatearmory.com/index.php/catalog/product/view/id/1239/category/4345/

http://palmettostatearmory.com/index.php/catalog/product/view/id/1555/category/53/

Or take some training with that 6720.

Rails can be great, but those magpul handguards are modular enough; you can mount what you need.

I wish I had kept my Midlength handguards and bought an Aimpoint PRO for it.

But you live and you learn.

I don't plan on another rail on an AR unless it was a precision rifle, meaning Bipod, sling, barrel and ammo that I'd see a difference out of free float, etc.

I'm also tempted to see how the Magpul SL handguards feel. They look to be similar to the VTAC rail in width and shape...

ETA 2: They look to help you not burnt your hands nearly as easy with a FSB as before as well. I like them; I want to handle first.

[breakingtime91]

Ok so here is my thought process on this carbine: Leight weight carbine that is more "modern" than the m4 I deployed with on my two afghan deployments (mostly just because lol)
so far this is what I'm thinking:
stock- b5 sopmod (tried it out on a friends rifle and like it alot)
mount/optic=daniel defense micro mount with a h1 riding on it
light/mount:thorntail offset/ sure fire g2
sling: either a duel QD or the proctor sling
pistol grip: friend is giving me a bcm gunfighter grip he has lying around (cant beat free)

*rail: this is where I'm conflicted. reading this thread I can see some of the guys I really respect consider it a benefit (Doc, chuck and a few more.) I'm currently looking at century c4 rail (free float two piece) or something like the KAC.

[BWT]

Ok so here is my thought process on this carbine: Leight weight carbine that is more "modern" than the m4 I deployed with on my two afghan deployments (mostly just because lol)
so far this is what I'm thinking:
stock- b5 sopmod (tried it out on a friends rifle and like it alot)
mount/optic=daniel defense micro mount with a h1 riding on it
light/mount:thorntail offset/ sure fire g2
sling: either a duel QD or the proctor sling
pistol grip: friend is giving me a bcm gunfighter grip he has lying around (cant beat free)

*rail: this is where I'm conflicted. reading this thread I can see some of the guys I really respect consider it a benefit (Doc, chuck and a few more.) I'm currently looking at century c4 rail (free float two piece) or something like the KAC.

If you're going to absolutely get a rail; I'd get a BCM key mod.

[breakingtime91]

would I have to take off the a frame to do that?

[tremiles]

would I have to take off the a frame to do that?

You would have to remove the fsb because it comes with a new proprietary barrel but, but you can shave it to clear the KMR while it's off and reinstall it to save some bucks.

Sent from my Nexus 4 using Tapatalk

[breakingtime91]

Hey, thanks guys. I think I am just going to run it with the original plastic and pick up a new light mount (like the one Jay runs) and then decide later on.

[BWT]

Hey, thanks guys. I think I am just going to run it with the original plastic and pick up a new light mount (like the one Jay runs) and then decide later on.

I think that's a great plan; because after shooting you may find things about the way you shoot that might help you make decisions.

Jay is teaching today, I might check back later.

[breakingtime91]

anyone know if a magpul section of rail (the five slot one) will fit the top of the standard hand guard that comes with the colt? I saw a video on youtube of a guy doing it. Only reason I ask is it would save me $55 bucks if i could use my already owned offset mount.

[breakingtime91]

also does anyone know if the thorntail offset would in someway hit the colt hand guard?

[LHS]

damn. Think I should still order one of these colt from PSA? srry for the questions but LHS has me questioning it now

Even I say grab it. For $800, you can buy a punch, stake the castle nut, and still be $200 ahead of the game.

[2alpha-down0]

The independent solutions I arrived at were
1) MI FSB light mount with QD socket
2) MI M4 stock QD attachment
3) see #1
4) I really got nothing


Add the GG&G SLiC Thing to that list. Pretty similar to the MI, but I prefer it (having owned both).

[Jay Cunningham]

Hmm, what do we have here?


2605

[JM Campbell]

MagPul goodies?

Sent from my SAMSUNG-SM-N900A using Tapatalk

[Jay Cunningham]

Ah, gear-whoring, er, I mean evaluation time!

2606

[JM Campbell]

What's in the baggie top of pic next to SKD sticker?

Sent from my SAMSUNG-SM-N900A using Tapatalk

[Default.mp3]

What's in the baggie top of pic next to SKD sticker?

Sent from my SAMSUNG-SM-N900A using Tapatalk

Free cherry flavored 5 Hour Energy SKD has been giving away with their orders.

http://i.imgur.com/pnIwsoYl.jpg

[HCM]

Add the GG&G SLiC Thing to that list. Pretty similar to the MI, but I prefer it (having owned both).

I have two of these, one of which is on my work rifle. I used some blue loc-Tite on the install and wintness marked the screw- so far so good a year and a half in.

[Jay Cunningham]

HOLY CRAP the handguards are a bitch to install!

[Jay Cunningham]

Initial thoughts on the MagPul stuff:

The HGs are A BITCH to put on! But I like them. I really like the stock. The pistol grip I'm a little disappointed with, the backstrap doesn't sit flush. I'm disappointed with the M-lok light mount because it doesn't extend far enough; the construction of it is fine besides that.

[BWT]

Initial thoughts on the MagPul stuff:

The HGs are A BITCH to put on! But I like them. I really like the stock. The pistol grip I'm a little disappointed with, the backstrap doesn't sit flush. I'm disappointed with the M-lok light mount because it doesn't extend far enough; the construction of it is fine besides that.

Are they thinner/rounder?

They look to be more oval shape. What would you say they're comparable to?

[Jay Cunningham]

They're as thin as they can be. I'd call them oval.

[Sasage]

Are there any places doing layaway on the 6720? Might be nice to have one on standby

[Jay Cunningham]

Someone posted a link earlier in the thread... don't know about layaway...

[Jared]

HOLY CRAP the handguards are a bitch to install!


This may be nothing worth mentioning but once I was talking on the phone with a rep from Midwest Industries asking why their drop in carbine rail was listed as "Colt Length" and "everybody else length" and which one did I need for this LMT. Rep told me that the Colt's were just a tiny bit shorter, and if you got the other one, you'd need two men and a boy to get it on. Since I was ordering for an LMT, I got the "everybody else" length. We tried to put that rail on a 6920 that belonged to my brother about a year later, and they flat would NOT go.

[Jay Cunningham]

Hmm...

I don't know what to say about that, other than the Colt guns are assembled per the TDP and the handguards are part of the TDP.

[JM Campbell]

Have you shot it yet with the new gizmos Jay? Impressions?
I have been thinking of another upper build using these parts.

[Jay Cunningham]

Not yet, I think tomorrow I'll get a chance. I'll take some pics too.

[JM Campbell]

Gracias Amigo!

I'm thinking of a 11.5-12.5 suppressed 556 upper with FSB (kind of KINO style) to go on my 6920 lower.

[Sadmin]

HOLY CRAP the handguards are a bitch to install!

Ha! I thought it was just me, I thought I might have to order a d-ring tool to get those damn things on. Really like them too.


Sent from my iPhone using Tapatalk

[Jared]

I don't know what to say about that, other than the Colt guns are assembled per the TDP and the handguards are part of the TDP.

That was my thought as well, just thought it might explain why the aftermarket handguards were so hard to put on. Maybe they are "everybody else" spec. Maybe the guy I talked to was full of it.

[Jay Cunningham]

2619

Starting to play.

[breakingtime91]

Got my 6720 the other day, I love the light weight. One interesting thing to note, when putting on the new pistol grip I encountered a problem of the grip not getting tight enough and the safety being to stiff (what I figured to be to much pressure on the spring). So instead of forcing it I backed it off and discovered metal shavings inside the hole for the screw. I was dumbfounded at first until I realized it was the shaving from when the lower was drilled out to accept the screw for the pistol grip. There were a bunch of very fine shavings that had broke lose from taking out and putting back in the screw. Its a strange QC error on colts part (not the end of the world but it was annoying) and I also learned something about the platform. Being my only personal experience before this was on a M4 in the marine corps I had never modified anything and didn't realize that the drilled out hole for the screw to the pistol grip is not sealed off from the trigger compartment. So I was surprised one a few of the shaving got in and around the safety itself and had to be cleaned out. I'll keep an eye on it about it appears that the metal shavings are no longer in the drill lines and the saftey appears to function as needed (function checked it several times).

And if that is normal when putting on a pistol grip, please let me know. I'm not worried about it, it didn't cause damage but its something to look out for.

[rob_s]

Normal? probably not, but it's always a good idea to clean out any hole before inserting a screw.

Hopefully it's from what you describe, and not due to cross-threading of the new screw on your part. I've done that before. I bought an appropriately-sized tap that I keep in my tool bag and when I change out grips I chase the threads with the tap and then spray out the hole with compressed air before putting in the new screw. Also, if you're using any of the aftermarket screws that come with thread locker glommed on them, it's a good idea to take a lighter and heat up the goop before you start the screw. Helps immensely. Magpul, in particular, really FUBARs their screws with the stuff.

[breakingtime91]

thanks for the reply rob!. I did not cross thread (looked and study it for awhile, extremely clean lines). BCM gun fighter comes with the exact same screw as the original A2 screw with no loctite so I decided to just use the original the first time. If it passes a function test and the grip is in tight, anything I should look for as a operational issue?
*I will now be cleaning out areas like that before installing something*

[rob_s]

One thing to check is how far the screw projects up into the lower, if at all. If the BCM came with the same screw you're probably ok, but Magpul (not to keep picking on them) comes with a different, shorter, screw for a reason. If the screw sticks up too high inside it can lock up the trigger mechanism.

[breakingtime91]

It does not, it is exactly the same as the A2 pistol grip screw, right down to the washer that they both have. If the trigger operates freely (I can watch it release the hammer with the upper off and my thumb on the hammer) and it resets fine that elevates that question right?

[rob_s]

Should be OK. My experience with dry function tests has been that they can expose some gremlins, but there are some that only come out during live fire. Sounds like you're good to go for that.

[rob_s]

Some parts here that really start to flush out the idea of the MOE SL 6720.

http://soldiersystems.net/2014/10/14/magpul-industries-new-m-lok-accessories-available/

I do find myself wishing that Colt would do the 6720 in a mid-length, only for the slightly longer handguard and possibility of spreading out the mounting area. I'd like to get a VFG, QD swivel mount, and base for an X300 on there. I suppose one could use the MOE Mlok VFG and QD swivel and an FSB mount for the X300.

[Jay Cunningham]

I'm not a genius or anything, I know that, so what the hell is up with all the different MS-1, MS-3, MS-4 sling stuff?

Can someone give me the louder-and-slower explanation for all the MagPul slings and sling hickeys?

[rob_s]

I don't fully grasp it either, but I think that as long as you're dealing with the current version of the sling they all start with the same base and different versions have different tails or attachments which you can slo a-la-carte. That's how I got around the confusion when I bought mine.

[archangel]

The MS-1 (http://store.magpul.com/product/MAG513/slings) is an adjustable 2 point, with just tri-glide buckles at the ends. You can attack it to existing sling loops, QD swives, etc, or get various (http://store.magpul.com/product/MAG519/slings) separate (http://store.magpul.com/product/MAG516/slings) adapters (http://store.magpul.com/product/MAG517/slings) to make it like the M-3 or -4.

The MS-2 (http://i115.photobucket.com/albums/n311/LaRueDeeko/S7000773.jpg) is their original single point / 2 point sling. Snap shackle to attach to the rear of the gun (via ASAP or similar), and lock-jaw clip to attach to the front of the gun (via RSA or similar) for 2 point, or the D ring on the sling for single point.

The MS-3 (http://store.magpul.com/product/MAG514/slings) is an updated version of the MS-4, with Magpul's para-clip (http://store.magpul.com/product/MAG541/slings) (updated version of the lock-jaw) on both ends. Can also be had with a single QD (http://store.magpul.com/product/MAG515/slings) on the rear-of-the-gun end.

The MS-4 (http://store.magpul.com/product/MAG518/slings) has QD on both ends.



There's also gen 1 and gen2 varieties of some of them. Gen 1 has a webbing loop on the adjuster, and you pull from the gun toward you to tighten. (And not sure how available the gen 1's are anymore) The Gen 2 has a flat plastic slider, with no loop, and you pull away from yourself to tighten (more like the VTAC and VCAS slings).

[rob_s]

Said another way...

This is what I see:
MS1® - Multi-Mission Sling (http://store.magpul.com/product/MAG513/slings)
-traditional 2-point
-rear attaches to/through stock slot
-front attaches to sling swivel
-various other tails, loops, swivels, or clips can be added to either end to customize the sling

The below all start with the MS1 as the base.

MS3® Sling GEN 2 (http://store.magpul.com/product/MAG514/slings)
-2-to-1-point convertible
-Rear attaches to ASAP® (http://store.magpul.com/product/MAG500/188) (via clip)
-Front attaches to MSA (http://store.magpul.com/product/MAG504/104)/RSA (http://store.magpul.com/product/MAG502/rails) (clip)


MS3® Single QD Sling GEN 2 (http://store.magpul.com/product/MAG515/slings)
-2-to-1-point convertible
-Rear attaches to ASAP®-QD (http://store.magpul.com/product/MAG529/188) (via QD swivel)
-Front attaches to MSA (http://store.magpul.com/product/MAG504/104)/RSA (http://store.magpul.com/product/MAG502/rails) (clip)


MS4® Dual QD Sling GEN 2 (http://store.magpul.com/product/MAG518/slings)
-2-to-1-point convertible
-Rear attaches to ASAP®-QD - Ambidextrous Sling Attachment Point (http://store.magpul.com/product/MAG529/188) (via QD swivel)
-Front attaches to MSA®-QD (http://store.magpul.com/product/MAG528/104)/RSA®-QD (http://store.magpul.com/product/MAG337/rails) (via QD swivel

[Jay Cunningham]

Oh okay. I guess I'd get an MS4 then.

[rob_s]

Oh okay. I guess I'd get an MS4 then.

that's basically what I did. Then I put QD sockets at the muzzle end, delta ring, castle nut, and stock body. I figure that gives me the most amount of flexibility possible.

https://scontent-b-iad.xx.fbcdn.net/hphotos-xpf1/v/t1.0-9/10534119_730623820328056_439536523516070079_n.jpg? oh=2b67699e689cb96cdd4bc382782c6094&oe=54B95596

[Jay Cunningham]

MagPul needs to fix their marketing on the sling stuff. I'm pretty well-versed in it, and I gave up trying to figure it out. I thought the MS1 was like the newest design revision and the other ones were obsolete or something.

[breakingtime91]

nice set up rob, no bs or frills. How you liking the BCM foregrip? I'm really lovin mine.