Best 12.5 barrel?

[BCP]

12.5” 5.56 NATO, all 10 shot averages. BCM 12.5” Barrel, Chrome-Lined, CLGS (Data from Eagle_19er)
55gr FMJ
IMI M193___________3028 fps
PPU M193__________2776
PMC XTAC XP193___ 2759
Winchester Q3131___ 2941
Federal XM193______2830
Federal AE223J_____ 2722
PMC Bronze 55gr____2712
Wolf Gold 55gr FMJ__2864
MEN M193 55gr_____2877
Norma TAC 223_____2833

62gr FMJ (M855, Clones)
IMI M855___________2827
PPU M855__________2812
PMC XTAC LAP______2801
Winchester Q3269___2780
Fed XM855-----------2842
Armscor 62gr FMJ----2668
Hornady Black 62gr---2739
Magtech First Def-----2785
GGG M855-----------2836

Fleet test data from US Army for the 14.5” M4/M4A1 in the early days with M855 was an average of 2920fps MV.

If you take the 14.5” M4 vs the 12.5” and look at the practical differences in effectiveness, it’s pole-vaulting over mouse turds.

14.5” M855 62gr 2920fps SA
100yds 2618fps 944ft-lbs
200yds 2336fps 751ft-lbs
300yds 2071fps 591ft-lbs

12.5” M855 62gr 2842fps SA
100yds 2545fps 892ft-lbs
200yds 2268fps 708ft-lbs
300yds 2007fps 555ft-lbs

If you’re shooting high volume training, I would lean on the barrel that lasts long and is reasonably accurate. To me, there isn’t much benefit in longer barrels in 5.56 because projectile weight and BC are so low. When you try to brute force it with velocity, but don’t have the propellant mass to support that, you just don’t see dramatic increases in performance that are meaningful downrange.

This is the main reason why 18” SPRs fell out of favor so quickly. Normal carbines and CQBRs with good triggers, free-float Block II SOPMOD rails, Mk.262, and good optics were plenty. SPR is still great for range work as a stable platform for learning trajectory and wind, but sucks to carry around.

The 12.5” velocities are negligible compared to 14.5” in practice, which is why I really like that barrel length. 14.5” turned out to be a lot faster than a lot of the gun rag experts proclaimed, and a lot of those articles had an agenda to push a new cartridge anyway.

If you ever see me buy anything longer than 12.5” 5.56, pay very close attention because something will need to have been so exceptional about the barrel to make me go longer. I’ve also been a big fan of 11.5” since the 1990s. My first 2 AR-15s I bought after the Colt AR-15A2 Sporter II in the 1980s, were 11.5” guns in the 1990s.

The problem is we're slaves to the 16" by law, if NFA weren't a thing then we'd see a ton of guys using shorter barreled ARs with suppressors on them for hunting, plinking etc.

 

[Constructor]

The problem is we're slaves to the 16" by law, if NFA weren't a thing then we'd see a ton of guys using shorter barreled ARs with suppressors on them for hunting, plinking etc.

Agree, now that the pistol brace rule has been changed I think the sale of shorter barrels will drop significantly.

 

[LRRPF52]

A few articles about terminal performance of bullets from DOC GKR and others relating velocity and barrel length.- edited to pick out a few paragraphs. Velocity matters, unless you're just shooting paper.

https://www.itstactical.com/warcom/ammunition/military-ammunition-failures-and-solutions/
https://www.justice.gov.za/comm-mrk/exhibits/Exhibit-JJJ-112.pdf
http://www.mlefiaa.org/files/ERPR/Terminal_Ballistic_Performance.pdf
https://www.realcleardefense.com/ar...ich_service_had_the_better_bullet_114140.html


"Criticism
There has been much criticism of the poor performance of the bullet on target, especially the
first-shot kill rate when the muzzle velocity of the firearms used and the downrange bullet
deceleration do not achieve the minimally required terminal velocity at the target to cause
fragmentation.[19] This wounding problem has been cited in incidents beginning in the first
Gulf war, Somalia, and in the current conflicts in Iraq and Afghanistan. In recent lab testing
of M855, it has been shown that the bullets do not fragment reliably or consistently from
round-to-round, displaying widely variable performance. In several cases, yawing did not
begin until 7–10 in of penetration. This was with all rounds coming from the same
manufacturer.[19] This lack of wounding capacity typically becomes an increasingly
significant issue as range increases (e.g., ranges over 50 m when using an M4 or 200 m when
using an M16) or when penetrating heavy clothing, but this problem is compounded in
shorter-barreled weapons. The 14.5 inches (37 cm) barrel of the U.S. military's M4 carbine
generates considerably less initial velocity than the longer 20" barrel found on the M16, and
terminal performance can be a particular problem with the M4.
Combat operations the past few months have again highlighted terminal performance
deficiencies with 5.56×45mm 62 gr. M855 FMJ. These problems have primarily been
manifested as inadequate incapacitation of enemy forces despite them being hit multiple times
by M855 bullets. These failures appear to be associated with the bullets exiting the body of
the enemy soldier without yawing or fragmenting.
This failure to yaw and fragment can be caused by reduced impact velocities as when fired
from short barrel weapons or when the range increases. It can also occur when the bullets pass
through only minimal tissue, such as a limb or the torso of a thin, small statured individual, as
the bullet may exit the body before it has a chance to yaw and fragment. "

"Unfortunately, combat operations since late 2001 have again highlighted terminal performance problems, generally manifested as failures to rapidly incapacitate opponents, during combat engagements when M855 62 gr “Green Tip” FMJ is fired from 5.56 mm rifles and carbines. This is not surprising, since M855 was not originally intended for use in carbines or rifles, especially those with short barrels."
"This failure of 5.56 mm bullets to upset can be caused by reduced impact velocities when hitting targets at longer ranges, as well as by the decreased muzzle velocity when using short barrel carbines. Failure to upset can also occur when bullets pass through minimal tissue, such as a limb or the torso of a thin, small statured individual, as the bullet may exit the body before it has a chance to upset. Finally, bullet design and construction plays a major role in reliable bullet upset. Without consistent bullet upset, wounding effects are decreased, rapid incapacitation is unlikely, and enemy combatants may continue to pose a threat to friendly forces and innocent civilians."

"These carbines had shorter barrels, usually around 14.5 or sixteen inches, which gave them lower muzzle velocity compared to the full twenty-inch barrel of the M16. The lower velocity of these carbines led to incidents such as those in Mogadishu where the M855 fired out of a CAR-15 failed to fragment and put targets down reliably.


The issue of M855 lethality continued to plague the military in the post-9/11 era. As the wars in Iraq and Afghanistan dragged on, the U.S. Army and Marines began to issue out M4 Carbines, which use a 14.5-inch barrel, in larger numbers. This only exacerbated the problem with M855. "

Terminal Ballistic Performance of the 5.56mm Cartridge
"If using a short-barreled weapon: The same guidelines apply as for barrier penetration loads. SBRs
usually have insufficient velocity to achieve fragmentation velocity."

I respectfully disagree with those claims, for the following reasons:

Every unit within JSOC and SOCOM started using shorter and shorter barrels after looking at all their AARs, formal ARDEC studies, and the pros and cons to barrel length. Even the USMC ditched their beloved 20” rifles in favor of Hk416/M27 IAR with 16” pipes, and MARSOC stayed in the SOCOM Block evolution approach with Block II and III with shorter barrels.

That old data about 5.56 performance has been so thoroughly debunked, I’m surprised to see it referenced in 2023.

We have a lot of data from 5.56 and 7.62 NATO performance even from early-on in GWOT, as well as large data studies done from Vietnam, Grenada, Panama, and Mogadishu. There are incidents were 7.62 NATO FMJ passed right through combatants at intermediate range, especially smaller trunk persons and healed-up as if they had never been shot. That isn’t the norm, but all of these cartridges are relatively small in bore diameter. They stacked enemy KIA like corkwood in Vietnam, Grenada, Panama, and Mogadishu with 10” to 14.5” barrels.

Grenada: Unit guys with Colt 653s (lightweight 14.5” barrels, guys with M203s have 20” M16A1s due to the lack of a 14.5” pencil barrel M203 combo, which was developed after Grenada for the Colt Commandos)

Panama, Colt 723s suppressed

Colt 723s with 14.5” barrel, Panama

Keep in mind that the units who saw the most combat in US history were Recon Teams in SOG out of Command and Control North. Their preferred weapon was the 11.5” XM177E2, colloquially referred to as the “CAR-15”.

There were no complaints of 5.56 terminal performance from those guys, or JSOC in the 1980s. Mark Bowden’s book, Blackhawk Down, made a big deal of it from one person’s anecdotes he interviewed. Guys in JSOC analyzed the Command & Control bird video footage and narrowed-in on the most vocal person who complained about M855’s lack of performance in Mogadishu, and saw that he wasn't even making his hits. Paul Howe and Chuck Pressburg have discussed that and the 5.56 vs 7.62 NATO debate.



But the old M14/7.62 NATO proponents, feeling validated in the long-held assertions about 7.62 vs 5.56, started furiously generating articles in the gun rags about how 5.56 is ineffective, especially from short barrels, and we had a resurgence of the “poodle shooter” mantra in the gun community/military service rifle cartridge debate that sounded alarm bells of impending doom for soldiers equipped with 5.56 carbines. What is interesting is that the units who shoot the most and enjoyed more than satisfactory results with 5.56 did NOT have this reaction. In fact, they started using shorter and shorter barrels.

For the Recce carbines in those units, used on Sniper Operations Teams, they wanted more accurate barrels, free-float, and compact Variable power optics to complement their M14s and SR25s, which were sparsely employed in the mix using an Arms Room approach (end-users plan and select their weapons configurations per the mission). This is where the select match Douglas and Lilja special-order pipes were installed by Unit Armorers with free-floated handguards even before the emergence of the ARMS and KAC rails.

They were shooting a lot of 69gr Match in a light DM carbine set-up well before the development of the Mk.262 77gr SMK OTM. Sinister would be a better source to pipe in here on the specifics of that history.

This thread is about 12.5” 5.56 carbines, which really don’t lose much to 14.5” carbines. There are 2 main categories of use for a 12.5” or 14.5" carbine:

1. Close Quarters work
2. Short to intermediate work

For #1, it almost doesn’t matter what bullet you use for terminal effects. M855 will canoe heads, perforate chests, fragment bone, and you’re shooting rapid strings anyway. Reliability is #1 priority for a CQB/CQM blaster in that application. I would have zero reservations about using M855 in-close because it doesn’t matter. M193 is fine as well. The subsequent bonded and other enhanced terminal performance bullets that have been specifically designed to provide lower impact velocity expansion have been described as particularly effective as well.

You can deal with #2 using better bullets with higher BCs, like the 70gr RDF (.416 G1), 73gr ELD-M, 77gr TMK, or 77gr RDF, with a good magnified optic on top. I like the numbers and form factor with the new wave of higher BC .224 bullets that are meant to be mag-COL compliant in the AR-15. If I had a 12.5” in a DM set-up or dual-role, I would back the truck up on whichever shot the best for the availability and price point I could get them.

I personally shoot 6.5 Grendel from 12” regularly (was just doing it this past weekend day/night/day along with multiple 5.56 DMRs, 18” Grendels, .223 bolt gun, and .308 Win) and when you see and hear the impact of 6.5mm on steel vs anything .224” at distance, it’s a no-brainer. There was one particular moment when one shooter was firing his 22” .223 Bolt gun with 77gr at the same target being shot with 12” Grendel and 123gr as I was spotting. I saw the little nick made by the .223 and then the big splash from the Grendel, with a “tink-DING” audible feedback. It was kind of comical in the moment.

The biggest question someone looking at 12.5” barrel length needs to answer is whether they will be shooting suppressed or not. If suppressed, I’m a fan of the MLGS. Next biggest question is whether they are going to just be using it for close work, or some frequent intermediate range shooting from 200-600yds. That will drive optics and barrel quality/accuracy/ammunition preference.

For me, the puny low-energy impacts on steel with .223 (even up at higher altitudes where the air is thin and in your favor) don’t really do much for me, so I basically am invested in whatever 5.56 blasters I already have with no real incentive to get any more.

 

[LRRPF52]

The problem is we're slaves to the 16" by law, if NFA weren't a thing then we'd see a ton of guys using shorter barreled ARs with suppressors on them for hunting, plinking etc.

ATF’s criminal conduct and infringements are taking a beating right now in the courts, so I don’t see their pistol brace fiasco holding water much after it’s renewed by the judicial branch. Their bureaucratic frame and receiver infringement was vacated on Friday last week. Their retard-level mental gymnastics don’t hold up even under basic judicial scrutiny.

My body is ready for the new pistol brace designs. Now is the time to snatch up short barrels on the market before it’s flooded with 16” AR-15 barrels I think.

 

[Constructor]

I see your photos and slanted charts and raise you a video...or 2...or 3


Buffman armor testing short and long barrels.
Personally I don't care what anyone uses, I have 12.5s that are faster than most 16s and 16s that are almost as fast as most 20s.
55fmjs for practice and MK318 and 62GDs for whatever crawls out of the gutter and into range. Knowledge is a valuable thing to those that can acknowledge they don't know everything.

I am curious that if velocity means nothing why do people move from a 308 to a 300 win mag or from a 7mm-08 to a 7mm mag? If velocity means nothing does BC also mean nothing and why people bother to compare cartridges by possible velocity. BTW the 6.8 is 100fps faster than the Grendel using the same weight bullet and same length barrel, they always compare a 24" Grendel to a 16" 6.8, wonder why?

 

[SolidCopper]

I’ve had good luck with Rainier arms 12.5 mid gas mountain fluted barrel, with or without suppressor.

Curious at the performance you’ve had. What kind of upper/hand guard are you using? Ammo you had the best luck with? I am considering one of these for work.

 

[LRRPF52]

I see your photos and slanted charts and raise you a video...or 2...or 3


Buffman armor testing short and long barrels.
Personally I don't care what anyone uses, I have 12.5s that are faster than most 16s and 16s that are almost as fast as most 20s.
55fmjs for practice and MK318 and 62GDs for whatever crawls out of the gutter and into range. Knowledge is a valuable thing to those that can acknowledge they don't know everything.

I am curious that if velocity means nothing why do people move from a 308 to a 300 win mag or from a 7mm-08 to a 7mm mag? If velocity means nothing does BC also mean nothing and why people bother to compare cartridges by possible velocity. BTW the 6.8 is 100fps faster than the Grendel using the same weight bullet and same length barrel, they always compare a 24" Grendel to a 16" 6.8, wonder why?

Nobody has said velocity means nothing. The reason for moving from .308 to .300 Win Mag is for long range (800-1400yds+) and same for 7mm-08 to 7mm Mag.

Not sure what you’re getting from 12” 6.8 but I’m seeing the following through multiple 12” Grendels:

12” 6.5 Grendel Faxon group buy barrels

90gr TNT Federal factory ammo (50rd boxes), 15ft from the muzzle
Unsuppressed
2702
2681
2670
2642
2654

2670avg 15ft, 2685mv

Suppressed
2675
2658
2660
2671
2685
2723
2700
2690
2682

2683 avg 15ft, 2698mv

107gr SMK on H335 2450fps

120gr Federal OTM Factory, .421 G1 BC
Unsuppressed
2360
2373
2374
2387
2384

Suppressed
2411
2398
2397
2349
2406
2384

15ft avg 2384fps
MV = 2393fps

I’ve never compared 24” Grendel velocity to 16” 6.8 SPC since it fails the Fairness aspect of critical thinking standards. I wanted 18” or 20” first, missed out on the "add to cart” frenzy at Midway in 2009, so I ended up with a 16” instead. I quickly saw that the velocities were the same or higher than what I was seeing on 6.8 Forums from 16” guns, which made me question why people were saying otherwise.

With 16” Grendel Enfield rifling in a Shaw beater pipe from AA, I was getting:
123gr A-MAX factory 2437-2456fps
123gr Scenar from Precision Firearms (.527 G1 BC) factory ammo: 2452fps
100gr NBT on 8208XBR: 2675fps
120gr SMK (.421 G1 BC) on TAC 2527fps
123gr A-MAX (.468 G1 Litz BC) on 31.2 CFE223 2504fps

My 17.6” and 18” Grendels with Lilja 3 Groove and 5R rifling basically duplicate the 16” with Enfield rifling.
123gr A-MAX on 31.2gr CFE223 avg 2490fps from the 17.6” Lilja
120gr Scenar-L factory (.497 G1 BC) avg 2511fps
Factory 123gr SST Hornady avg 2457fps
107gr SMK on 8208XBR 2655fps

No matter what you do to the 6.8 though, you don’t have any bullets that have .420 to .615 G1 BCs, with the exception of the 130gr NBT at .433 G1 BC, 130gr Berger at .452 G1 and 140 Berger at .487 G1. Looking at 20”-24” Hodgdon and Western Powders data for 6.8 SPC/SPC II, with 130gr Berger and 130gr NBT....

Hodgdon’s 24” barrel
130gr Berger on LT-30 2347fps

Accurate Powders 20” barrel
130gr NBT on AA5744 2345fps
130gr NBT on AA1680 2196fps
130gr NBT on AA2200 2434fps
130gr NBT on X-Terminator 2269fps

General consensus among 6.8 guys was that the 130gr NBT is too slow, doesn’t expand well for hunting since it’s meant for .270 Win. They’re also about twice the price of 123gr ELD-M in 6.5mm for hand loaders. Bergers are of course more expensive as well, only to have a slow Grendel with a 20” 6.8 barrel and limited magazine loading options that will allow longer COL.


In 6.5mm, the 107gr SMK through 130gr RDF cover the .420 to .615 BC range.

The BC makes a difference even in the closer ranges, so the higher BC projectile will overtake the lower ones even if the lower BC bullets are fired a bit faster at the muzzle.

The other factor that is important for me is wind drift. I shoot a lot of steel at distance. 400yds is boring to shoot unless it’s a KYL rack.
This past weekend, we were making 1st-round hits at 760yds and 800yds with 12” and 12.5” Grendels, and 2nd-round hits at 900-1000yds with 18” Grendels on 12” and 18” plates.

I regularly shoot the 12” Grendel out to 800yds with factory ammo in varying wind conditions, and haven’t even hand-loaded for it after all these years.

This is why every time I get a little interested in building a 12” 5.56, I ask what it will do for me that I already don’t have, and can’t answer that other than it being 5.56 with 30rd mags. 5.56 is great for the close fight, but is really anemic as you get beyond 200-300yds, even from 18”SPRs.

 

[Constructor]

Most 6.8 guys are hunters not snipers, they don't care much about BCs or shooting paper at 800yds.

 

[LRRPF52]

Most 6.8 guys are hunters not snipers, they don't care much about BCs or shooting paper at 800yds.

Steel at 800yds, not paper. If you could have a PDW-sized blaster that does both, why not?

You can buy or load any of the dozens of factory ammo for hunting and TGT, many of which will do both really well.

That same blaster can be used for Home Defense, a truck gun, hogs, deer, and recreational long range shooting with very positive results on steel when you impact, that you can see yourself through your optic, unlike with .308 Winchester.

That’s the appeal to me at least.

 

[Constructor]

Rather than you saying what velocity you get and me saying what I get I would rather used published sources that can be verified. As you can see from the Hornady ammo pages they use a 24" Grendel barrel and a 16" 6.8 barrel. At a gain or loss of apx 25fps/inch we can subtract 200 from the Grendel or add 200 to the 6.8 to get to a common equal barrel length and velocity using Hornady factory ammo.
https://www.hornady.com/ammunition/rifle/6-8mm-spc-120-gr-sst#!/
https://www.hornady.com/ammunition/rifle/6-5-grendel-123-gr-sst#!/
With handloads I can push a 110gr to 2800 out of a 16" and a 120 to 2700 out of a 16". Maj Holland, AMU gunsmith Cris Murray and balistician Troy Lawton said when they developed the 6.8 they could get a 115gr Hornady up to 2800 out of a 20". Many said that was hype but we proved it was not hype IF the barrels are made correctly and that was the whole goal when we started trying to fix all of the problems with the 6.8. The bore area of the Douglas barrels was correct and what the SAAMI spec was based on. When everyone jumped on manufacturing barrels they made cheap 6 groove barrels that did not meet the bore area spec. That along with the reamers from PTG that had a number transposed led to blown primers and all the BS that followed. In the end it turned out to be a great hog round.

As for the long high BC bullets not expanding in the 6.8 it is the same for the Grendel, all of those long high BC bullets were designed for faster cartridges like the 260 and 6.5x55 so they don't expand for the Grendel either.

 

[LRRPF52]

I think you meant MSG Steve Holland, not Maj Holland. There was no Major Holland associated with the 6.8 SPC.

In the early days, there was a meeting where senior enlisted SEAL weapons development proponents were present with Remington engineers and asked them if they could get a 115gr to 2900fps. Remington engineers didn’t even check and just said, “Yeah, sure!” That was out of 16”. This was of course unachievable. SOCOM across the different communities was looking for a DMR cartridge in the AR-15 receiver set, so guys wouldn’t have to lug around an SR-25. 115gr BC doesn’t cut it for a DMR since the BC is so low, which affects wind drift.

Long high BC bullets expand plenty fine in 6.5 Grendel, even from short barrels.

129gr SST does it very well with repeated results for the past 20 years now.
2350fps mv keeps it over 1800fps out to 350yds

130gr Berger Hunting VLD expands fine at Grendel velocities within common hunting distances.
2350fps mv keeps it over 1800fps out to 400yds at sea level.

129gr ABLR especially expands rapidly and is ideal for short barrels. (1300fps expansion threshold)

This feels like a 2010 conversation all over again. This stuff has all been demonstrated and validated for many years now.

I think the guys that developed 6.8 really missed an opportunity by going with the wrong bore diameter. They should have moved the case length back a little bit, used a 30˚ shoulder, and gone with the .257” bore and projectiles, with a new TGT OTM from Sierra for the DMR role. Do a 110-115gr SMK with better sectional density and BC in the mid .4s to low .5s.

.277” was 2 steps too far up through .264” from .243”. It’s nice for hunting for frontal area impact with more blunt ogives, but not good for a DMR and carbine cartridge. Also notice how one of these kids is not like the other, and they submitted a de-tipped V-MAX to FBI Ballistics lab and tried to pass it off as an OTM like the others when doing the FBI terminal ballistics requirements in hopes for sign-off for LE applications.

The development of the 6.8 SPC was plagued with missteps, lack of professionalism, misconduct, and unjustified insular behavior to people who were trying to help them with bore diameter selection based on generations of Ordnance Board, CONARC, and ARDEC developmental test history. It’s fine for a close range hunting cartridge, but really missed the mark for what SOCOM was looking for.

 

[Constructor]

Bill Waites one of the main guys of the Grendel forum around 2010 posted a photo on barfcom of a 120gr TSX recovered from a deer he shot, the bullet had not expanded even 30% and several others chimed in with other bullets that did not expand. So yeah it's easy to say all of those high BC bullets work fine but anyone with any experience knows different. You are known for posting a photo of 160 .264 bullets and saying they all work as designed, we know that isn't true. You say it's all a win but many that aren't Grendel fanboys have shown many bullets do not expand as designed at range. The point is velocity matters. The links I posted here are from Fackler and DOC GKR that are experts and they say bullets do not fragment or yaw at lower velocity out of SBRs. There have been countless studies on it proving it, they even have photos LOL. Sure a 22LR will kill but a smart man wouldn't choose a 22LR or bullets that do not expand (hunting)or fragment as designed unless you are just shooting targets.

There is a place for MK18s and other SBRs but it's CQB where a small maneuverable weapon is more important than terminal performance. If the task is killing hogs at night with thermal and fairly close range then I'll choose a 12.5" 6.8, it uses faster burning powders and is more efficient due to the case capacity to bore area ratio. It develops velocity faster in short barrels. Yes I have been a fan of the 6.8 since early 2006, about 6 months after I broke my first Grendel bolt but I can say most of us 6.8 users know not to use bullets that weigh more than 130gr in the 6.8 because a muzzle velocity of under 2400 isn't a good thing.
The military didn't choose the 6.8 or 6.5, that is telling enough. Glad I'm a wildcatter and can make whatever I want.
Sorry no photos or charts for you today, I have ammo to load.

 

[Chicory01]

A few articles about terminal performance of bullets from DOC GKR and others relating velocity and barrel length.- edited to pick out a few paragraphs. Velocity matters, unless you're just shooting paper.

https://www.itstactical.com/warcom/ammunition/military-ammunition-failures-and-solutions/
https://www.justice.gov.za/comm-mrk/exhibits/Exhibit-JJJ-112.pdf
http://www.mlefiaa.org/files/ERPR/Terminal_Ballistic_Performance.pdf
https://www.realcleardefense.com/ar...ich_service_had_the_better_bullet_114140.html


"Criticism
There has been much criticism of the poor performance of the bullet on target, especially the
first-shot kill rate when the muzzle velocity of the firearms used and the downrange bullet
deceleration do not achieve the minimally required terminal velocity at the target to cause
fragmentation.[19] This wounding problem has been cited in incidents beginning in the first
Gulf war, Somalia, and in the current conflicts in Iraq and Afghanistan. In recent lab testing
of M855, it has been shown that the bullets do not fragment reliably or consistently from
round-to-round, displaying widely variable performance. In several cases, yawing did not
begin until 7–10 in of penetration. This was with all rounds coming from the same
manufacturer.[19] This lack of wounding capacity typically becomes an increasingly
significant issue as range increases (e.g., ranges over 50 m when using an M4 or 200 m when
using an M16) or when penetrating heavy clothing, but this problem is compounded in
shorter-barreled weapons. The 14.5 inches (37 cm) barrel of the U.S. military's M4 carbine
generates considerably less initial velocity than the longer 20" barrel found on the M16, and
terminal performance can be a particular problem with the M4.
Combat operations the past few months have again highlighted terminal performance
deficiencies with 5.56×45mm 62 gr. M855 FMJ. These problems have primarily been
manifested as inadequate incapacitation of enemy forces despite them being hit multiple times
by M855 bullets. These failures appear to be associated with the bullets exiting the body of
the enemy soldier without yawing or fragmenting.
This failure to yaw and fragment can be caused by reduced impact velocities as when fired
from short barrel weapons or when the range increases. It can also occur when the bullets pass
through only minimal tissue, such as a limb or the torso of a thin, small statured individual, as
the bullet may exit the body before it has a chance to yaw and fragment. "

"Unfortunately, combat operations since late 2001 have again highlighted terminal performance problems, generally manifested as failures to rapidly incapacitate opponents, during combat engagements when M855 62 gr “Green Tip” FMJ is fired from 5.56 mm rifles and carbines. This is not surprising, since M855 was not originally intended for use in carbines or rifles, especially those with short barrels."
"This failure of 5.56 mm bullets to upset can be caused by reduced impact velocities when hitting targets at longer ranges, as well as by the decreased muzzle velocity when using short barrel carbines. Failure to upset can also occur when bullets pass through minimal tissue, such as a limb or the torso of a thin, small statured individual, as the bullet may exit the body before it has a chance to upset. Finally, bullet design and construction plays a major role in reliable bullet upset. Without consistent bullet upset, wounding effects are decreased, rapid incapacitation is unlikely, and enemy combatants may continue to pose a threat to friendly forces and innocent civilians."

"These carbines had shorter barrels, usually around 14.5 or sixteen inches, which gave them lower muzzle velocity compared to the full twenty-inch barrel of the M16. The lower velocity of these carbines led to incidents such as those in Mogadishu where the M855 fired out of a CAR-15 failed to fragment and put targets down reliably.


The issue of M855 lethality continued to plague the military in the post-9/11 era. As the wars in Iraq and Afghanistan dragged on, the U.S. Army and Marines began to issue out M4 Carbines, which use a 14.5-inch barrel, in larger numbers. This only exacerbated the problem with M855. "

Terminal Ballistic Performance of the 5.56mm Cartridge
"If using a short-barreled weapon: The same guidelines apply as for barrier penetration loads. SBRs
usually have insufficient velocity to achieve fragmentation velocity."

This is regarding M855 which everyone knows, sucks.

Most people using 10.3-12.5 are running TMK/TSX/Gold Dot/Fusion. Very reliable fragmentation and expansion from 300-420 yards in these lengths.

 

[Constructor]

This is regarding M855 which everyone knows, sucks.

Most people using 10.3-12.5 are running TMK/TSX/Gold Dot/Fusion. Very reliable fragmentation and expansion from 300-420 yards in these lengths.

I bet most are using M193 and m855 just like everyone else.

 

[Hoody2shoes]

I use bullshit 55gr whatever for cqb drills. I use mk262's for literally everything else

 

[Constructor]

Tested another 14.5" 5R barrel today, ave 130fps faster than the 14.5" BCMs I have tested. I'm good with people thinking velocity doesn't matter.

 

[Hoody2shoes]

I think I posted this already but to reiterate
My 12.5 core gets around 2630 at the muzzle with mk262's w/o the can and 2650 w/ the can.

 

[Chicory01]

I see your photos and slanted charts and raise you a video...or 2...or 3


Buffman armor testing short and long barrels.
Personally I don't care what anyone uses, I have 12.5s that are faster than most 16s and 16s that are almost as fast as most 20s.
55fmjs for practice and MK318 and 62GDs for whatever crawls out of the gutter and into range. Knowledge is a valuable thing to those that can acknowledge they don't know everything.

I am curious that if velocity means nothing why do people move from a 308 to a 300 win mag or from a 7mm-08 to a 7mm mag? If velocity means nothing does BC also mean nothing and why people bother to compare cartridges by possible velocity. BTW the 6.8 is 100fps faster than the Grendel using the same weight bullet and same length barrel, they always compare a 24" Grendel to a 16" 6.8, wonder why?

Which 12.5's do you have that are as fast as a 16? Noveske Stainless?

 

[MikeMiller]

Thread is a great read

When it comes to barrel advice I am going with Frank Green since I have a cabinet filled with State, National and World Championship medals won with his barrels. I am a very minor player compared to the many many big wins with Franks barrels

Before anyone says anything I paid retail for every one of those barrels

 

[Constructor]

Which 12.5's do you have that are as fast as a 16? Noveske Stainless?

Blackstone Arms sells the 5R barrels.

 

[Charmingmander]

Blackstone Arms sells the 5R barrels.

AR Performance used to sell a 3R barrel. Wonder what that did for velocity.

 

[Zolar]

I've been very happy with my Noveske Crusader barrel

 

[TonyTheTiger]

AR Performance used to sell a 3R barrel. Wonder what that did for velocity.

AR Performance and @Constructor are one and the same. Blackstone Arms is who he sold the business to if I understand correctly.

 

[Charmingmander]

AR Performance and @Constructor are one and the same. Blackstone Arms is who he sold the business to if I understand correctly.

No kidding! Would definitely love to hear more then.

 

[JJ3]

AR Performance used to sell a 3R barrel. Wonder what that did for velocity.

Interested also. May have missed it but what kind of precision are these barrels producing?

 

[346ci]

You would need a top tier barrel like a bartlein to out perform them.