Colt M4A1 SOCOM Barrel Accuracy: Another Look

[Molon]

Colt M4A1 SOCOM Barrel Accuracy: Another Look


https://www.ar15.com/media/mediaFiles/28568/colt_m4a1_with_kac_ras_handguard_001-1881912.jpg


In 2010, I posted one of the first publicly available, in-depth accuracy evaluations of a Colt M4A1 SOCOM barrel. At that time, the Colt SOCOM barrel was relatively new to the civilian market. Many people, including myself, were pleasantly surprised by the level of accuracy/precision that I obtained with the SOCOM barrel; particularly since it is a chrome-lined, NATO chambered “military-grade” barrel. Since that time, the Colt M4A1 SOCOM barrel has developed a significant appreciation amongst AR-15 enthusiasts.


The M4A1 SOCOM barrel

https://www.ar15.com/media/mediaFiles/28568/colt_m4_socom_barrel_01_resized-1305762.jpg


https://www.ar15.com/media/mediaFiles/28568/colt_m4_socom_barrle_02_rsized-1305763.jpg



More recently, I assembled another upper receiver group based on the Colt M4A1 SOCOM barrel. This new build features a Colt cage-code marked M4 upper receiver, a Colt “C” marked bolt carrier group and a 13” Geissele MK14 M-LOK free-float hand-guard.


https://www.ar15.com/media/mediaFiles/28568/colt_socom_21d_resized-1305765.jpg



A genuine Colt M4A1 SOCOM barrel is 14.5” long and has a medium contour; it is not an HBAR. The barrel has a 5.56mm NATO chamber and a 1:7” twist.

Colt SOCOM barrel

https://www.ar15.com/media/mediaFiles/28568/stripped_socom_barrel_02_resized-1305778.jpg



Colt HBAR

https://www.ar15.com/media/mediaFiles/28568/colt_16_inch_hbar_6721_02-1305761.jpg




A genuine SOCOM barrel has the typical M4 circumferential cut-out located approximately 1.4” forward of the gas block for the attachment of an M203 grenade launcher, as well as rectangular shaped cut-outs underneath the hand-guards on the port and starboard sides of the barrel, located approximately 1.4” aft of the gas block, for the same reason. The gas port on a genuine SOCOM barrel has a diameter of 0.062” and the barrel employs a carbine-length gas system.


The SOCOM barrel has a stripped weight of 1 pound, 14 ounces. That is only 2 ounces heavier than the ubiquitous 16” government profile barrel found on the Colt 6920.

Colt SOCOM barrel

https://www.ar15.com/media/mediaFiles/28568/stripped_socom_barrel_02_resized-1305778.jpg



Colt 6920 barrel

https://www.ar15.com/media/mediaFiles/28568/Colt_16_inch_government_profile_6920_bar-1305760.jpg



The stripped weight of the SOCOM barrel is 5 ounces heavier than the stripped weight of the standard Colt 14.5” M4 barrel. The pic below shows the difference between the standard M4 barrel and the SOCOM barrel. From the gas block journal forward, the two barrels are identical


SOCOM barrel on top, standard barrel on bottom

https://www.ar15.com/media/mediaFiles/28568/socom_barrel_comparison_to_standard_m4_b-1305776.jpg



The next pic is a close-up comparing the two barrels in the area between the chamber and the gas block journal, showing you where the extra weight is added.



https://www.ar15.com/media/mediaFiles/28568/socom_barrel_comparison_02-1305775.jpg



The date-code on my original SOCOM barrel was “11/03” and the date-code on my newer SOCOM barrel is “02/18”


https://www.ar15.com/media/mediaFiles/28568/date_code_fro_socom_barrel_01-1305768.jpg


https://www.ar15.com/media/mediaFiles/28568/new_socom_barrel_date_code_01_resized-1305773.jpg




My original SOCOM barrel had an “F-marked” front sight base. Colt no longer stamps an “F” on their front sight bases, but their newer front sight bases maintain the length of 1.98” from the top of the barrel to the shelf for the front sight post.



https://www.ar15.com/media/mediaFiles/28568/f_marked_front_sight_base_of_socom_barre-1305770.jpg



https://www.ar15.com/media/mediaFiles/28568/f_marked_front_sight_base_comparison_21-1305769.jpg



My original SOCOM barrel was stamped:

“C MP 5.56 NATO 1/7”



The newer SOCOM barrel is stamped with Colt’s cage code.

“13629 M P 5.56 NATO 1/7”



https://www.ar15.com/media/mediaFiles/28568/socom_barrel_stamp_01_resized-1305777.jpg



https://www.ar15.com/media/mediaFiles/28568/new_colt_socom_barrel_stamp_01_resized-1305772.jpg



Both of these SOCOM barrels have the “O” stamp near the chamber portion of the barrel. Naturally, the M4A1 SOCOM barrel has M4 feed ramps.


https://www.ar15.com/media/mediaFiles/28568/0_stamp_for_socom_barrel_01-1305759.jpg



https://www.ar15.com/media/mediaFiles/28568/m4_feed_ramps_of_socom_barrel_01-1305771.jpg



Accuracy Conmparison


In 2010, my original SOCOM barrel with the “11/03” date-code produced a 10-shot group fired from a distance of 100 yards that had an extreme spread of 0.90”. That group was fired from my bench-rest set-up using match-grade hand-loads and a high magnification scope.



https://www.ar15.com/media/mediaFiles/28568/colt_socom_barrel_10_shot_group_at_10_ya-1305767.jpg



My newer SOCOM barrel with the “02/18” date-code produced a 10-shot group fired from a distance of 100 yards that had an extreme spread of 0.93”. This group was fired off of sand-bags using match-grade hand-loads and a high magnification scope.



https://www.ar15.com/media/mediaFiles/28568/colt_socom_2020_10_shot_group_at_100_yar-1305766.jpg


. . . .

[AndyLate]

Put me down as one of the folks surprised at the accuracy displayed in your original testing. It honestly made me reconsider everything I "knew" about issued small arms built by the lowest bidder.

I appreciated your original evaluation and appreciate the update. Its nice to see Colt still knows how to build a barrel.

Andy

[gaijin]

One of my “grab this one” carbines has a SOCOM barreled upper with Kahles LPVO.

Appreciate your effort Molon. I’ve never achieved your degree of accuracy/precision from mine, but I’ve never used dialed in handloads nor High Mag. Scope.

[markm]

I'm a sucker for a SOCOM barrel. My Minniesmachine and BCM are my go to guns. I see them pop up in EE, but some goofball has either chopped the FSB, permed the Flash hider or Both. :mad:

I shoot my SOCOM with TA01NSN from 100-600 yards every weekend as a ritual.

[Slater]

If the SOCOM barrel was an actual HBAR profile instead of a medium contour, do you think that would make any appreciable difference in overall accuracy and/or durability?

[DG23]

I'm a sucker for a SOCOM barrel. My Minniesmachine and BCM are my go to guns. I see them pop up in EE, but some goofball has either chopped the FSB, permed the Flash hider or Both. :mad:

I shoot my SOCOM with TA01NSN from 100-600 yards every weekend as a ritual.

Bought my MMC SOCOM based on your comments here...


Definitely owe you a few beers. :)

[DG23]

If the SOCOM barrel was an actual HBAR profile instead of a medium contour, do you think that would make any appreciable difference in overall accuracy and/or durability?

Not really an 'apples to more heavy apples' comparison as the barrel length and twist rates are not the same between them.

The profile alone is not the only difference there...

[Hammer_Man]

Thanks for the post Molon! It’s amazing how consistently precise these barrels are. Makes me want to build another!

[markm]

Bought my MMC SOCOM based on your comments here...


Definitely owe you a few beers. :)

I shot it yesterday. It's literally my favorite AR. Goes out every weekend.

[ASH556]

I've posted this in a similar thread on TOS, but it's probably worth sharing here too. First of all, Colt SOCOM barrels are the Jam! I've had 4 or 5 of them, all with shaved FSB's under Geissele rails. The combo just works! The first couple had TA11 ACOG's on them; one with a horseshoe, the other with a chevron. Here are 10 shot 100yd groups from those:

https://live.staticflickr.com/65535/52550057913_c3cdc30f6d_b.jpg
https://live.staticflickr.com/65535/52549976420_6e22306d39_b.jpg
https://live.staticflickr.com/65535/52549976425_7410291f11_b.jpg

I rearranged a bunch of things and these are my current starters. One is a 14.5" Colt SOCOM with a Nightforce NX8 and the other is an 11.5 Colt HRT with a TA01NSN and a piggybacked RM06. I had the NX8 with the RM06 piggybacked on the 11.5, but it was pigish with the can (m4-2000) and I never made good use of the NX8, only really ever going up to 4X with it. ACOG's have great glass and if you're only going to use 4X, may as well make it a smaller, lighter, and cheaper 4X. I moved the NX8 over to this 14.5, which was wearing a T2, and put it in a 1.93 height NF Ultramount. That taller mount really made the optic come alive for me. All of a sudden I had less trouble getting behind in in 8X and on 1X it really became red dot fast whereas before it felt slow, hence I had the RMR piggybacked.

This newest iteration (and a different barrel than the others pictured above) still shoots lights out. This is 10rds at 100yds with the NX8 on 8X (the center dot is 1.25MOA) with Hornady 75gr Match. I pulled one round just a little bit and saw it in the scope. Still, an impressive performer.

https://live.staticflickr.com/65535/52506524081_6c8d64851b_b.jpg
https://live.staticflickr.com/65535/52514520636_7a60994212_b.jpg
https://live.staticflickr.com/65535/52515004785_643515dace_b.jpg

[rojocorsa]

What about these barrels makes them so accurate?

[markm]

What about these barrels makes them so accurate?

I'd guess good QC and a beefy profile. Heavy profile is less load sensitive. Colt also had legendary accuracy with the 6940 (I think). The monolithic upper with carbine gas system. It wasn't a heavy barrel, but had a different barrel nut system.