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Posted: 3/2/2021 6:40:34 PM EDT
[Last Edit: Molon]
Colt M4A1 SOCOM Barrel Accuracy:  Another Look





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








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.






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





Colt HBAR






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





Colt 6920 barrel





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





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.







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










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.











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”











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.










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.







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.






. . . .
Link Posted: 3/2/2021 6:52:33 PM EDT
[Last Edit: TGWLDR] [#1]
Awesome info. Happy to see that accuracy is comparable given the timespan.

Thanks.


@Lancelot

Any chance of getting this thread tacked?
Link Posted: 3/2/2021 6:54:21 PM EDT
[#2]
Great post as always, Molon.
Link Posted: 3/2/2021 7:17:51 PM EDT
[#3]
A decade and the man only loses .03 MOA.

Dude is a machine.
Link Posted: 3/2/2021 7:39:35 PM EDT
[#4]
Originally Posted By Molon:
Colt M4A1 SOCOM Barrel Accuracy:  Another Look


https://www.ar15.com/media/mediaFiles/28568/colt_m4a1_socom_upper_receiver_group_21-1305764.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, 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 hand 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


. . . .
View Quote

Thank you sir. I'm involved in a Colt M4A1 SOCOM build now. My barrel
is dtd 11/19 I think. Using a "C" stamped upper and KAC M4 RAS, Warcomp FH
but a 1B1B6 stamped BCG.

I'm glad to know the barrel is still GTG

Thanks again.
Link Posted: 3/2/2021 7:56:20 PM EDT
[#5]
Thanks!
Link Posted: 3/2/2021 8:57:43 PM EDT
[#6]
Excellent as always!  This is great as I have my 2nd SOCOM build underway now.  Thanks for all the info, someday when it all gets complied into The Book of Molon I want a copy!


Link Posted: 3/2/2021 9:00:45 PM EDT
[#7]
I've loved Colt socoms since I bought one and had similar accuracy results. Great write up, love the content new and old Molon.
Link Posted: 3/2/2021 9:42:01 PM EDT
[#8]
Great info!

Thanks for the work and time involved.
Link Posted: 3/2/2021 10:05:57 PM EDT
[#9]
You are the man and those Colt barrels always impress me
Link Posted: 3/3/2021 1:13:14 AM EDT
[#10]
Great info to have. I’m curious to see what kind of accuracy the 6921 govt profile 14.5” barrel has given the same conditions.
Link Posted: 3/3/2021 2:30:53 AM EDT
[#11]
Great info as always, Molon.
Link Posted: 3/3/2021 2:33:48 AM EDT
[#12]
Are these things in stock anywhere?
Link Posted: 3/3/2021 3:30:49 AM EDT
[#13]
Molon is back?

Take notes teeners, ARFCOM stock is going up.
Link Posted: 3/3/2021 5:42:22 PM EDT
[#14]
Thanks for doing this review! I bought a complete 6721 after reading some of your reviews of the barrel and it's accuracy potential.
Link Posted: 3/3/2021 8:23:00 PM EDT
[#15]
I wonder if the FN SOCOM barrels are also as accurate?
Link Posted: 3/3/2021 8:57:16 PM EDT
[#16]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Theodoric:
I wonder if the FN SOCOM barrels are also as accurate?
View Quote

I've heard from more than one that it's an apples to apples comparison.


No personal experience. I've been wanting to add an FN for awhile now to see for myself.
Link Posted: 3/3/2021 9:17:31 PM EDT
[#17]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By WIZZO_ARAKM14:
Great info!

Thanks for the work and time involved.
View Quote

Link Posted: 3/3/2021 9:36:18 PM EDT
[#18]
Molon!!!! I though you were gone. Love reading your reviews!
Link Posted: 3/4/2021 4:59:03 PM EDT
[#19]
@Molon

Sir, your contributions are invaluable.  Your posts switched me on to the SOCOM barrel about 6 years ago and I've built several rifles for myself and friends using them.  I also appreciated some of your testing combining the Colt SOCOM barrel and 62gr Gold Dot.  That combo has become a staple for me and I have used it to good effect.  

Here is the zero confirmation target from the last one I built about a year ago using a Trijicon TA11 3.5X ACOG with Chevron Reticle and 62gr Speer Gold Dot:





Another earlier gun, different SOCOM barrel, same 62gr Gold Dot, using a TA11H.  I found the chevron reticle I owned later to be easier to be precise with than the center dot of this horseshoe

Link Posted: 3/4/2021 5:14:29 PM EDT
[#20]
Arfgods need to add an "AWESOME " button in thread rating.
Link Posted: 3/4/2021 6:35:54 PM EDT
[#21]
Link Posted: 3/5/2021 10:14:13 PM EDT
[#22]
i have a Socom that shoots very well. they are really good. i can post pics.
Link Posted: 3/5/2021 10:50:06 PM EDT
[#23]
All mine are now pinned SOCOM's. I have 1 16" BCM still.  Very accurate for me.
That group was fired from my bench-rest set-up using match-grade hand-loads and a high magnification scope.
View Quote

I'd like to see these tests with standard issue ammo & optics.
Link Posted: 3/5/2021 11:46:35 PM EDT
[#24]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By urbankaos04:
Are these things in stock anywhere?
View Quote

This. I’m trying to stock up on a couple barrels but can’t find any of these. I’m tempted to go the fan route.
Link Posted: 3/6/2021 3:07:49 AM EDT
[#25]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By fuzzy03cls:
All mine are now pinned SOCOM's. I have 1 16" BCM still.  Very accurate for me.

I'd like to see these tests with standard issue ammo & optics.
View Quote
Gonna be similar to his M193 clone article.

Near 1 MOA mean radius and 3 MOA extreme spread.
Link Posted: 3/6/2021 3:19:28 AM EDT
[#26]
Link Posted: 3/6/2021 5:05:05 PM EDT
[#27]
Awesome as always. Thank you.
Link Posted: 3/6/2021 9:19:16 PM EDT
[#28]
Excellent as always.  Great to see you back Molon!

I’ve got several SOCOM barrel builds and I’ve gotten great service from them.
Link Posted: 3/6/2021 10:32:58 PM EDT
[#29]
My findings M4 Colt SOPMOD barrel with M855A1
DR M855A1 Accuracy test
Link Posted: 3/7/2021 12:45:42 AM EDT
[#30]
Help a new guy, can you buy a rifle built with this barrel from the factory now?
Link Posted: 3/7/2021 3:31:57 PM EDT
[#31]
where can i get Surefire flash hider ?
Link Posted: 3/14/2021 6:29:51 PM EDT
[#32]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Bullseye_Doc_Holiday:
 

Here is the zero confirmation target from the last one I built about a year ago using a Trijicon TA11 3.5X ACOG with Chevron Reticle and 62gr Speer Gold Dot:

https://i.imgur.com/oc7RMcR.png

https://i.imgur.com/ibeHsbr.jpg

Another earlier gun, different SOCOM barrel, same 62gr Gold Dot, using a TA11H.  I found the chevron reticle I owned later to be easier to be precise with than the center dot of this horseshoe

https://i.imgur.com/y2dcBLkl.jpg
View Quote


Strong work!  

..
Link Posted: 3/27/2021 11:06:07 AM EDT
[Last Edit: Sinister] [#33]
My son just shot his fifth or sixth Army Small Arms Championships.  This year everyone fired a rack-grade M4A1 and either an M9 or M17 all week.

The M4A1s should all have SOCOM-profile barrels and A1 triggers by now (with the exception of USASOC weapons which will have Geissele Select-Fire triggers).  The first rifle match is shot with Matech back-up irons (!), everything else with an ACOG, Aimpoint, or EoTech.  No carry handles as they are all issued with Matechs now.

The iron-sight combat course starts at 400 yards and finishes at 100, again, an M4A1 and the Matech.  A high score (standing at 200 yards) is in the high-80s (on the modified E-type silhouette, which is NO JOKE as far as how small that 5- and X-ring is).



All shooters fire standard 62-grain GI M855A1 issued on the line.  Since that's generally not available for off-duty practice I found the Sierra 69-grain Tipped Match King flies closest to M855A1.  Haven't done a whole lot of other experimenting but I've loaded Sierra and Nosler 69s as well.  M855A1 bullets are the same length as Sierra 77s, but lighter -- they tend to start getting blown around a bit by wind at 400, where the Sierra 77 is still relatively un-bothered.

Here is a visual comparison for those looking to match/duplicate M855A1 exterior flight ballistics in M4geries and M16s.  I've used Varget, TAC, and IMR 8208 to get fairly close to matching the BDC reticle in a TA01B ACOG.  The Sierra 77s have a little better weight, so you might want to stick with the 69 TMK or maybe the Berger to match velocity decay.

Attachment Attached File

Link Posted: 3/27/2021 12:36:57 PM EDT
[#34]
Sinister, you never tried the 60gr TMK?
Link Posted: 3/27/2021 12:38:20 PM EDT
[Last Edit: Sinister] [#35]
Nope, couldn't find any with the covid panic.  :(

The 69 TMKs were gifted by our (National Match) barrel-maker.  All our data was gathered from GI (SOCOM-barreled) M4s and 16-inch mids.

My kid said he was spoiled using a free-floated mid with Geissele SSA.  Had very short prep-time this year and the shorter carbine sight radius, Matech, and A1 GI trigger were a challenge, so I've built him a carbine using a new (Colt) SOCOM barrel and ALG trigger (got them from Midway) for practice / data-gathering.



69 Sierras and Nosler match HPBTs are shorter than the M855A1, so the "Shorter, blunter" ogives are also a close stand-in (given the weight difference).

Attachment Attached File
Link Posted: 3/27/2021 12:48:30 PM EDT
[#36]
Good reports from all.

CD
Link Posted: 3/27/2021 2:50:18 PM EDT
[#37]



The Sierra 60 grain Tipped MatchKing has a nominal length of 0.899".  The G1 ballistic coefficients are:

>  .323 @ 2700 FPS and above
>  .313 between 1950 and 2700 FPS
>  .283 between 1700 and 1950 FPS
>  .253 @ 1700 FPS and below


...
Link Posted: 3/27/2021 5:33:37 PM EDT
[Last Edit: Sinister] [#38]
I wish I could find some to compare how they fly against M855A1.

I'd bet they're close as well, considering the A1's steel insert length and mid-rear center of gravity.

Thank you!
Link Posted: 3/27/2021 5:46:10 PM EDT
[#39]
Colt SOCOM barrels are awesome.
Link Posted: 3/28/2021 11:44:45 PM EDT
[#40]
Also check out his Mk262 clone playlist.




CD
Link Posted: 4/3/2021 10:40:19 PM EDT
[Last Edit: Molon] [#41]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By fuzzy03cls:
I'd like to see these tests with standard issue ammo . . .
View Quote


I haven't done any formal testing of M193 clones with this barrel, however, I did shoot a rapid-fire 20-shot group with this barrel using MEN 56 grain M193 at a distance of 100 yards.  That group had an extreme spread of 1.67".








...
Link Posted: 4/4/2021 3:15:45 AM EDT
[#42]
That’s pretty damn good.
Link Posted: 4/7/2021 3:56:15 PM EDT
[#43]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Combat_Diver:


https://www.youtube.com/watch?v=v9PAV6jx2zM


CD
View Quote



So, three 10-shot groups had an average extreme spread of 2.58".  That's hardly the match-grade accuracy, that some people have claimed that they're getting with this ammunition.



...
Link Posted: 4/7/2021 4:10:30 PM EDT
[Last Edit: cvtrpr] [#44]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Theodoric:
I wonder if the FN SOCOM barrels are also as accurate?
View Quote

I shot a 192-5x (out of 200 possible at 500y) on the Army Modified NMC course with an FN M4A1 at All Army three weeks ago; my total score was 454-5X.  Funny thing, I shot no X's at 200 and 300.  
Link Posted: 4/7/2021 4:12:16 PM EDT
[#45]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Sinister:
My son just shot his fifth or sixth Army Small Arms Championships.  This year everyone fired a rack-grade M4A1 and either an M9 or M17 all week.

The M4A1s should all have SOCOM-profile barrels and A1 triggers by now (with the exception of USASOC weapons which will have Geissele Select-Fire triggers).  The first rifle match is shot with Matech back-up irons (!), everything else with an ACOG, Aimpoint, or EoTech.  No carry handles as they are all issued with Matechs now.

The iron-sight combat course starts at 400 yards and finishes at 100, again, an M4A1 and the Matech.  A high score (standing at 200 yards) is in the high-80s (on the modified E-type silhouette, which is NO JOKE as far as how small that 5- and X-ring is).

https://www.pistoleer.com/shooting-targets/pics/eic.gif

All shooters fire standard 62-grain GI M855A1 issued on the line.  Since that's generally not available for off-duty practice I found the Sierra 69-grain Tipped Match King flies closest to M855A1.  Haven't done a whole lot of other experimenting but I've loaded Sierra and Nosler 69s as well.  M855A1 bullets are the same length as Sierra 77s, but lighter -- they tend to start getting blown around a bit by wind at 400, where the Sierra 77 is still relatively un-bothered.

Here is a visual comparison for those looking to match/duplicate M855A1 exterior flight ballistics in M4geries and M16s.  I've used Varget, TAC, and IMR 8208 to get fairly close to matching the BDC reticle in a TA01B ACOG.  The Sierra 77s have a little better weight, so you might want to stick with the 69 TMK or maybe the Berger to match velocity decay.

https://www.ar15.com/media/mediaFiles/18978/M855A1_Comparison_jpg-1881892.JPG
View Quote

@sinister

I shot the EIC matches there, too.  Is your son AC, RC or NG?
Link Posted: 4/7/2021 4:42:30 PM EDT
[#46]
He's active now, but shot with-against the guys in the Texas National Guard the last five years when he was a cadet.
Link Posted: 4/7/2021 4:52:56 PM EDT
[#47]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Sinister:
He's active now, but shot with-against the guys in the Texas National Guard the last five years when he was a cadet.
View Quote

I was coaching for the NG teams that were there.  I have some quite good friends who shoot for the Texas team (one I went to HS with).  
Link Posted: 4/7/2021 5:07:09 PM EDT
[#48]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Theodoric:
I wonder if the FN SOCOM barrels are also as accurate?
View Quote
I now have a Colt SOCOM and an FN SOCOM in my possession, but have absolutely zero precision rounds stocked to test with, so I have no way of telling you
Link Posted: 4/7/2021 5:29:42 PM EDT
[#49]
Thanks again and again for the time you put into your posts for our benefit.
It is very much appreciated.
Link Posted: 4/22/2021 8:08:04 PM EDT
[Last Edit: Molon] [#50]
Discussion ForumsJump to Quoted PostQuote History
Originally Posted By Sinister:
I wish I could find some to compare how they fly against M855A1.
View Quote


The Sierra 64 grain Tipped GameKing also looks promising.





Ballistic coefficients:

>  .323 @ 1900 fps and above

>  .305 between 1500 and 1900 fps

>  .270 @ 1500 fps and below


...
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