View Full Version : American Rifleman Article about M855A1 and Mk318.....
MadAngler1
05-23-14, 11:15
I know there is a topic about M855A1 in the terminal ballistics forum, but I felt it was appropriate to start a new thread.
First, did anyone read the article in the June edition of American Rifleman? It's by Major John Plaster. The question I had regards his contention that a 1/9 twist is better for M855A1 rounds as opposed to a 1/7 twist. He quotes accuracy data. This sort of took me by surprise, given the length of the M855A1 bullet and its 62 grain weight. I realize 1/9 twist is better for 55 grain rounds, but I figured there wouldn't be much difference for 62 grain rounds (as opposed to 75 and 77 grain rounds, where a 1/7 twist is necessary). Thoughts?
I'm glad he talked about the increased chamber pressures of the M855A1 round. I think we're going to be seeing some premature bolt wear and port erosion with this round for certain (as the author mentions). Ultimately, we can thank the Clinton administration's quest for a lead free round for all of this crap, but it's a shame the Bush administration did nothing to stop it. I think the Mk318 is a better choice for a barrier blind round no doubt, but it's not like troops can pick between the Mk318 and Mk262 for whatever mission they go on.
All of the above would be fixed by a 6.8 SPC chambered rifle of course, or issuing more SCAR-Hs :p
This article? (http://www.americanrifleman.org/articles/testing-army-m855a1-standard-ball-cartridge)
MadAngler1
05-23-14, 12:04
This article? (http://www.americanrifleman.org/articles/testing-army-m855a1-standard-ball-cartridge)
yep. sorry, i forgot to add a link. I have the paper copy
ad_infinitum
05-27-14, 21:12
Interesting article.
The question I had regards his contention that a 1/9 twist is better for M855A1 rounds as opposed to a 1/7 twist...
I was curious about this, too.
My understanding was that the extra long steel-core bullets would become instable if they weren't fired with anything less than a 1:7 twist...
LMT Shooter
05-28-14, 01:34
I was curious about this, too.
My understanding was that the extra long steel-core bullets would become instable if they weren't fired with anything less than a 1:7 twist...
I believe the article says that the M856 tracer required the 1/7 twist to be stabilized, and that M855 was GTG with 1/9, which is also what I had always heard previously. I was shocked at the margin of greater accuracy 1/9 vs. 1/7, with M855, he stated he found in his testing.
Interesting to see the RETARDATION that went into this Goat Rope cartridge. Increasing the pressure to get this stupid round where they want is about as dumb as it gets.
Also interesting to see how the 1/7 hurt the accuracy of the SS109 bullet.
Interesting to see the RETARDATION that went into this Goat Rope cartridge. Increasing the pressure to get this stupid round where they want is about as dumb as it gets.
Also interesting to see how the 1/7 hurt the accuracy of the SS109 bullet.
Agreed. It is beyond belief that our military would spend that much $ to develop ammo that operates at that high pressure, will break bolts, and will render ACOGs ineffective at longer ranges. Great job.
Ultimately, we can thank the Clinton administration's quest for a lead free round for all of this crap, but it's a shame the Bush administration did nothing to stop it.
The round has been in development since 1999 or earlier? So it took the military TEN YEARS to develop M855A1?
According to another article:
"The Army launched the M855A1 program in September 2005 as a Congressionally mandated initiative to replace the lead core M855 cartridge."
http://www.defensemedianetwork.com/stories/new-u-s-army-5-56-rounds-head-to-afghanistan/
In the 2005, both houses of Congress were Republican controlled and a Republican was in the White House.
It's kind of hard to blame Clinton/dems/libs in this case.
Interesting article...
I wonder why would anyone want to increase the already too high chamber and port pressure in the M4, for a marginal gain in performance.
The improvement of the M885A1 over M855 is that you have a much larger and better steel penetrator, AND a reliably fragmenting bullet with no angle of attack issues and less dependant on impact velocity. All this without using an open tip, exposed lead, or an expanding design, so still complies with the letter of Hague.I guess designating a bullet "match grade" doesn't hurt, either, no matter what is the reality. The bullet performance would be pretty much the same at slightly lower velocities (remember, the chamber pressure increases exponentially compared to muzzle pressure).
Interesting article...
I wonder why would anyone want to increase the already too high chamber port pressure in the M4, for a marginal gain in performance.
I think the idiots wanted the trajectory to match M855 as closely as possible. We run ACOGs all the time with everything from 55s to 77s and adjust on the fly. I'd rather have a reasonable pressure round and adjust my COG hold accordingly. Tying the ACOG's reticle to the poor performing M855 was the first mistake. Just dumb on top of dumb.
Regardless of who was in control of the legislature when, etc.... we know where this retarded nonsense is rooted.
The most perplexing thing is that this M55A1 load has a bullet which most likely has a slightly higher BC than M855, so lowering the muzzle velocity (which is also higher in the M855A1) would actually make the two trajectories more similar.
The flyers mentioned in the article are likely due to the complex construction (leading to offset axial center of balance), and the probably the jacket crimps with some variability onto the steel nose, that's why some presentations say that it is OK if some nose movement is noticed.
I'd love to get a few hundred of these bullets to play with. No way in hell would I fire this loaded round in any of my guns though.
Failure2Stop
05-28-14, 12:54
I believe the article says that the M856 tracer required the 1/7 twist to be stabilized, and that M855 was GTG with 1/9, which is also what I had always heard previously. I was shocked at the margin of greater accuracy 1/9 vs. 1/7, with M855, he stated he found in his testing.
Yeah, the stated precision drop with the 1:9 vs 1:7 is inconsistent with the testing data I have seen.
Yeah, the stated precision drop with the 1:9 vs 1:7 is inconsistent with the testing data I have seen.
Same here. On the other hand who really puts time into shooting M855 groups with multiple barrel twists to catch this type of thing?
Tying the ACOG's reticle to the poor performing M855 was the first mistake. Just dumb on top of dumb.
We only had several hundreds of millions of rounds carried in magazines and ASPs both theaters and several tens of billions of rounds in the war stocks at the time.
We only had several hundreds of millions of rounds carried in magazines and ASPs both theaters and several tens of billions of rounds in the war stocks at the time.
Yeah... I understand that. I guess the idea that M855 ever made it as the standard load is frustrating. I have and old magazine with an article just like this one... but on the subject of going from M193 to M855.
An OTM is the right answer. The specialized units have figured this out. This M855a1 projectile has some positives however.
Yeah, the stated precision drop with the 1:9 vs 1:7 is inconsistent with the testing data I have seen.
This is the part that I don't understand...
I though that extremely long .224 bullets like 75-77gr. match bullets and these 62gr steel core bullets would fail to stabilize adequately in anything less than a 1:7 or 1:8 twist barrel?
They made the M855A1 bullet even longer, and it's somehow OK (or even better) in a 1:9 barrel?
Same here. On the other hand who really puts time into shooting M855 groups with multiple barrel twists to catch this type of thing?
Back in the day, the swiss did their tests and chose a 1-10" twist for their Sig 556 because of better accuracy. They do have a proprietary 5.56 (63 gr lead core, non fragmenting) load, but I've read a chilean paper (their state factory, FAMAE, builds the Sig 550/556) where they tested true M855/SS109 and got best accuracy out of 1-9 or 1-10 barrels. I've shot pulled M855/SS109 bullets in 1-10 barrels and they do group very well, so it is no surprise that M855A1 groups well in 1-9 barrels.
Back in the day, the swiss did their tests and chose a 1-10" twist for their Sig 556 because of better accuracy. They do have a proprietary 5.56 (63 gr lead core, non fragmenting) load, but I've read a chilean paper (their state factory, FAMAE, builds the Sig 550/556) where they tested true M855/SS109 and got best accuracy out of 1-9 or 1-10 barrels. I've shot pulled M855/SS109 bullets in 1-10 barrels and they do group very well, so it is no surprise that M855A1 groups well in 1-9 barrels.
Wow. For years I've been drinking the M4C.net kool-aide and thinking that anything less than a 1:7 twist was inadequate... now it turns out that 1:9 or 1:10 is just fine?!
Is the fetish about 1:7 just because that's USGI?
IIRC, 1-7" is needed to have adequate stabilization with tracer rounds (very long) and artic (very dense air) conditions.
Yep. We can get M856 to fly straight/stabile in a 1/9, but it's warm thin air in the desert.
Failure2Stop
05-28-14, 14:43
To accurately test the effect of rifling twist rate on the precision of the projectile it would require several identically manufactured, identically chambered, precisely rifled test barrels. I do not see that having been done for the purposes of the article.
Add to that the fact that chamber dimensions play a significant part in precision with regard to specific loads, and the reported result is nothing but a slice of anecdotal speculation.
There are simply too many possible variables to try to assign fault in the twist rate at such low testing densities.
Show a real test under controlled conditions by an impartial testing facility/personnel and I will be willing to give it more weight.
Very true...
The same could be said about the POI change between M855 and M855A1 in this test.
Failure2Stop
05-28-14, 15:31
Results of M855 in 1:7 and 1:9 barrels from someone I trust:
Prior to the firing of the M855, control groups were fired from the test barrels using match-grade handloads seated with Sierra 55 grain BlitzKings. The 10-shot control group fired from the 1:7” twist barrel had an extreme spread of 1.17” and the 10-shot control group fired from the 1:9” twist barrel had an extreme spread of 0.89”.
Three 10-shot groups were fired from the upper with the 1:9” twist barrel in the manner described above. The extreme spreads for those groups measured:
2.72”
2.19”
2.24”
for a 10-shot group average of 2.38”. The three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 0.76”.
In the same manner as above, three 10-shot groups were fired from the upper with the 1:7” twist barrel. The extreme spreads of those groups measured:
2.14”
3.01”
1.71”
for a 10-shot group average of 2.29”. As before, the three 10-shot groups were over-layed on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for this composite group was 0.68”.
Molon?
In any case, the quality of the barrel is still a great variable.
Molon?
In any case, the quality of the barrel is still a great variable.
For sure. You can take this to unlimited extremes.... i.e. what powder was used in the baseline match load? Maybe one barrel fouled into the M855 powder differently, etc.
But I take that test as a reasonable indicator of what to expect.
IIRC, 1-7" is needed to have adequate stabilization with tracer rounds (very long) and artic (very dense air) conditions.
I believe the American Rifleman article indicated 1:7 was necessary to stabilize tracer rounds.
If you ask people that shoot benchrest (extreme accuracy), they would probably opt for the slower twist that stabilizes the bullets they expect to use, under the expected conditions.
But I'm sure you all know there is very little, if any, difference in accuracy between 1-10, 1-11 and 1-12 barrels in 308 with normal bullets. I would expect about the same in 5.56.
If you ask people that shoot benchrest (extreme accuracy), they would probably opt for the slower twist that stabilizes the bullets they expect to use, under the expected conditions.
Yep. Our bolt rifle smith is rooted in that Benchrest mindset. Slowest twist that will stabilize the bullet you shoot.
LMT Shooter
05-31-14, 00:28
Yeah, the stated precision drop with the 1:9 vs 1:7 is inconsistent with the testing data I have seen.
It is something I have never heard or read anywhere else before, but Maj. Plaster is far more experienced than I am, or probably ever will be.
LMT Shooter
05-31-14, 02:10
Wow. For years I've been drinking the M4C.net kool-aide and thinking that anything less than a 1:7 twist was inadequate... now it turns out that 1:9 or 1:10 is just fine?!
Is the fetish about 1:7 just because that's USGI?
I've read a lot of reviews/tests where folks got good accuracy from 75/77gr lead core bullets in 1:8-1:10 barrels. I had a 1:9 barrel that shot 75gr lead core bullets to MOA. YMMV
I do think there may be a bit of a USGI "fetish" about it. I am prepared to be stoned &/or burned at the stake for this heresay.
My 1/9 M&P barrel shoots 77gr SMK's just fine at 100yds. Any further and it might tumble, no idea, never tried it. I measured the twist a while back and it was very close to the stated 1/9, so I can see how these work in a non 1/7 barrel.
It's not a very scientific test, but my 1/9 M&P barrel shoots 77gr SMK's just fine at 100yds. Any further and it might tumble, no idea, never tried it.
I'd bet that most 1/9 barrels 14.5 or longer will stabilize 77s fine. An 11.5 might start to struggle. Contrary to what I always used to think, velocity helps stability... increased RPMs I guess.
I'd bet that most 1/9 barrels 14.5 or longer will stabilize 77s fine. An 11.5 might start to struggle. Contrary to what I always used to think, velocity helps stability... increased RPMs I guess.
Higher velocity and a slower twist are definitely interchangeable. I think everyone is just caught up in the 1/7 mil-spec craze.
From everything I read, I kind of expected the bullets to tumble, explode, and cause global warming from anything slower than 1/8.
Now here's the question: at what distance do you start to notice the difference between 1x9 and 1x7 w/ 77's for accuracy, if at shorter ranges the differences aren't as apparent? I gather the entire point of the 77 is to get more reach, correct?
Now here's the question: at what distance do you start to notice the difference between 1x9 and 1x7 w/ 77's for accuracy, if at shorter ranges the differences aren't as apparent? I gather the entire point of the 77 is to get more reach, correct?
IMO, if you have two identical match grade barrels with the two respective twist rates, the 1/7 might get a bit more reach before the bullet loses stability. Since, theoretically, velocity and twist are interchangeable, as the bullet loses velocity downrange, it will lose stability. With a faster initial RPM, it retains enough rotation for a longer period of time to keep it stable. This is just my theory, YMMV.
Longer reach isn't the entire reason for heavier bullets, but it is part of the equation. More energy downrange, better wind bucking ability/higher BC.
After reading this, I plan on pushing some 77gr SMK's through my 1/9 CL barrel as far as I can when I get the chance. It may not be the most accurate barrel, it is CL after all. My 1/8 match barrel shoots them like a dream though.
We shoot a 20" 1/9 bolt gun past 1000 yards all the time with 77s. It won't lose stability even hundreds of yards beyond effective range.
We shoot a 20" 1/9 bolt gun past 1000 yards all the time with 77s. It won't lose stability even hundreds of yards beyond effective range.
You have the velocity working in your favor with a 20" barrel since a velocity can make up for a slower twist. Given, it's not a huge difference, but it could be just enough compared to a 14.5/16" barrel.
I have noticed bolt guns generally have a slower twist compared to AR-15's, which is possibly due to the longer barrel/higher velocity.
Yep. The velocity helps I think. We don't have any shorter 1/9s to try.
These last couple posts convince me that the obsession with a 1:7 twist is just a fetish.
Given that virtually none of the self-proclaimed "high speed, low drag" guys here are shooting past several hundred yards or shooting tracers, I can't understand the insistence on a 1:7 twist...
These last couple posts convince me that the obsession with a 1:7 twist is just a fetish.
Given that virtually none of the self-proclaimed "high speed, low drag" guys here are shooting past several hundred yards or shooting tracers, I can't understand the insistence on a 1:7 twist...
I have to agree. Unless barrel length is less than 14.5", I don't see a need for 1:7 twist for most purposes. If I were shooting 80g and heavier bullets out of 16" and longer barrels, then I can see the need for barrel twist faster than 1:8.
If I were shooting 80g and heavier bullets out of 16" and longer barrels, then I can see the need for barrel twist faster than 1:8.
We've shot the Sierra 80 gr SMK out to 1000 yards with the 1/9 bolt gun mentioned above. To both of your points... 1/8 would cover everything up to 80 gr in any barrel length. 1/7 is faster than what 99.9% of the people shooting it need.
We've shot the Sierra 80 gr SMK out to 1000 yards with the 1/9 bolt gun mentioned above. To both of your points... 1/8 would cover everything up to 80 gr in any barrel length. 1/7 is faster than what 99.9% of the people shooting it need.
Thanks for sharing your experience. I am trying to decide on a barrel twist rate for shooting a .223 in F Class competition.
There are guys shooting as fast as 1/6.5 twist barrels in some set ups. Not sure if that's F class stuff... but they're running those 90gr bullets, and know what and why they're doing it.
One thing to keep in mind is your altitude. A stabile twist for a long bullet at one altitude isn't the same at another altitude. That said, 1/8 is still a solid choice.
I think 1/8 is the perfect compromise for most modern day semi-auto 5.56/.223 applications. Sionics got it right!
I wonder if 1/7 was chosen by the military to still be effective after tens of thousands of rounds that is typical of service rifles...?
I wonder if 1/7 was chosen by the military to still be effective after tens of thousands of rounds that is typical of service rifles...?
The 1:7 makes sense for the military, because they might actually shoot tracer rounds that need it, just like the M4 barrel contour makes sense for them, on the off chance that they might attach a grenade launcher.
For us weekend warriors, who are not going to shoot tracers, and who are never ever going to mount a grenade launcher, neither makes much sense, except for fetishizing everything the Pentagon approves...
Yep. That M856 is a very long bullet.... 1/7 does indeed just fall into the "mil-spec" obsession.
The 1:7 makes sense for the military, because they might actually shoot tracer rounds that need it, just like the M4 barrel contour makes sense for them, on the off chance that they might attach a grenade launcher.
For us weekend warriors, who are not going to shoot tracers, and who are never ever going to mount a grenade launcher, neither makes much sense, except for fetishizing everything the Pentagon approves...
Ah, yeah, I forgot about those guys. Those tracers are some loooonnng bullets.
I too read the article in American Rifleman. It’s much more lengthy in the paper version. I’m curious if this round is available to the public, and if so, who is selling it? I’d like to buy a box or two to test against some M855 just for the fun of it.
Failure2Stop
06-02-14, 15:43
If all you're going to shoot is 55 gr blaster ammo, the 1:9 is fine.
If you are going to use a shorty, modern long projectiles (such as the all copper bullets that are highly effective in tissue), or in temperature and elevation extremes, I wouldn't go any slower than 1:8, and I can tell you that it's going to be easier to find 1:7 offerings than 1:8 offerings for shorty's and "duty" use.
Yeah. I'd like to take some apart. Maybe fire it in a bolt gun. It sounds like it'd be rough on steel targets.
Howdy,
These last couple posts convince me that the obsession with a 1:7 twist is just a fetish.
Given that virtually none of the self-proclaimed "high speed, low drag" guys here are shooting past several hundred yards or shooting tracers, I can't understand the insistence on a 1:7 twist...
+1!
For the civilian market it just a marketing scam.
I grew up turkey hunting with a Win 12ga pump w/ a 30" full choke barrel. Back in the 90's Remington started the las test fad in turkey hunting using a 19.5" barrel.
It was just a marketing scam to get people to buy a new shotgun.
Nowadays the Remington turkey guns all have 24" barrels.
The short barrels were a joke and you gave up 100 to 200ft/sec over a 28-30" barrel and 25yds for effective range.
Paul
If you are going to use a shorty, modern long projectiles (such as the all copper bullets that are highly effective in tissue)...
OK, this makes more sense. I can imagine that a 10" or 11" barrel would give up enough velocity to have a hard time stabilizing longer bullets at anything less than 1:7.
... or in temperature and elevation extremes...
Now I'm confused... the problem is denser air, right? So, the "extremes" are low altitude and extremely cold temperatures, right?
That is, heat or high altitudes make a faster twist rate superfluous, right?
... I can tell you that it's going to be easier to find 1:7 offerings than 1:8 offerings for shorty's and "duty" use.
I know that just about everything out there is 1:7, I'm still just wondering why the conventional wisdom here (M4C.net) seems to regard 1:9 like herpes, when it sounds like it's perfectly adequate for for 100% of the shooting that most of us are going to do (no tracers, no long range shooting in arctic temperatures, "normal" barrel lengths, etc.).
Failure2Stop
06-05-14, 07:26
Now I'm confused... the problem is denser air, right? So, the "extremes" are low altitude and extremely cold temperatures, right?
If your stability is based on hot/warm conditions (very important if using a suppressor) and the temperature drops, the stability factor drops, potentially unsafely so (most common condition extreme).
Same for altitude, humidity, and barometric pressure.
Temperature is generally a bigger issue as it causes physical changes in components, powder burn-rate, and bore concentricity with suppressors, not just issues with the air being thicker.
[/quote]That is, heat or high altitudes make a faster twist rate superfluous, right?[/quote]
Eh, kinda, but not always in accordance with air density math.
I know that just about everything out there is 1:7, I'm still just wondering why the conventional wisdom here (M4C.net) seems to regard 1:9 like herpes, when it sounds like it's perfectly adequate for for 100% of the shooting that most of us are going to do (no tracers, no long range shooting in arctic temperatures, "normal" barrel lengths, etc.).
I would say that 1:9 does 90% of what most users will do with their 5.56 guns, but then again, so will airsoft or an M&P 15-22.
One of the issues with 1:9 is that they were generally (with a few exceptions of course) chambered in .223, and put out by less than well regarded companies. They had numerous issues, with the twist rate being another check in the box of "not what I want".
Yeah.... knowing that I shoot mostly 75-77 gr stuff in ARs, and mostly carbine/shorter barrels.... Given 1/9 or 1/7, all else equal, I'm going to error on the side of 1/7. If 1/8 was an option, I'd pick that.
MadAngler1
06-06-14, 23:59
The round has been in development since 1999 or earlier? So it took the military TEN YEARS to develop M855A1?
According to another article:
"The Army launched the M855A1 program in September 2005 as a Congressionally mandated initiative to replace the lead core M855 cartridge."
http://www.defensemedianetwork.com/stories/new-u-s-army-5-56-rounds-head-to-afghanistan/
In the 2005, both houses of Congress were Republican controlled and a Republican was in the White House.
It's kind of hard to blame Clinton/dems/libs in this case.
It was under the Clinton administration that the quest for an "environmentally safe" round began. The article goes into this, but I guess the web version is missing some of the key points the paper copy has. p. 60 of the June 2014 American Rifleman notes the "Joint Service Non-Toxic Ammunition Working Group" as started in 1995. The M855A1 is the four version of a "lead free" projectile for the Army's AR-15 variants. Of course, the Republicans want to be environmentalists as well, and GWB's administration didn't help matters in failing to kill this stupid, costly project. I am deeply disturbed that the Army is using a round with a significantly higher pressure that causes more wear and tear on M4 carbines, especially when the Mk318 is a perfectly acceptable alternative without the downsides of the M855A1.
I'm glad Failure2Stop (Jack) posted Molon's old data. Molon would generally use a Colt HBAR 20" or M4 16" chrome-lined barrel for a lot of those tests (and he had a Krieger barrel on one of his guns as well). He would use the Blitzkings for a control load to great effect. I was shocked that the article claimed 1/9 twists stabilized 62 grain bullets better, because it flies in the face of Molon's data, along with many others whom have tested these rounds in various barrels. Without a doubt, 1/7 twist is necessary for stabilizing the 75 and 77 grain OTM loads that have proven their worth. It is also needed for the longer Barnes TSX 62 grain loads that work quite well on hogs. Molon would also publish stuff regarding gyroscopic stability factor, and how, although you may get good groups at 100 yards out of a 1/8 or 1/9 twist barrel, 1/7 twist ensures terminal effectiveness beyond that (meaning the bullet will fragment and yaw appropriately in flesh beyond 100-200 yards, before the round drops below its effective velocity).
Regardless, I think everyone here should get themselves a paper copy of this article. By no means is it pro-M855A1. If anything, it condemns it. It shows a true failure of leadership amongst officers and civilians in the Dept of Defense to stop dangerous crap from happening in the armed forces. Our guys should be using Mk318 or Mk262, unless something better comes along. Lead is a poison, but it should not be done away with when it comes to ammo.
It was under
Regardless, I think everyone here should get themselves a paper copy of this article. By no means is it pro-M855A1.
Well the article does claim the military ended up with a better round. But it will boil the blood of the bullshit intolerant.
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