Questions about M855A1

[sinister]

All M4A1s come with the heavier barrel now and yes, it's pretty impressive what we're seeing out of rack-grade carbines and M16s. Add a float tube/rail, a Geissele trigger, and decent glass and you've got a significant advantage over an equivalent gun and shooter using M855.

[vicious_cb]

Armor is only part of it, and honestly probably the lesser part. Realistically, M855A1 probably doesn't have much more in the way of armor piercing capability than M855 does. It can't penetrate plates, so all that it would do better than M855 in that arena is piercing Kevlar at range. So maybe an extra 50 meters where it will still pierce Kevlar, where an M855 wouldn't?

The big deal is barrier penetration. It does great at penetrating hard barriers. So window glass, car doors, heavy metal doors, etc. Just any number of things you find in urbanized places that people like to use for cover.

And it can't be stressed enough that its increased penetration is only one improvement over M855. Mainly it's going to tumble and fragment out of any barrel at any range, and it's probably twice as accurate out of a decent barrel. There are people who claim it can do sub MOA from a SOCOM barrel, which, if true, would put it up there with just about any match grade bullet out there.

And again, it does all this at the same cost as M855, so roughly 35 cents a round. Even if it had no increased barrier penetration, a sub .50 cent bullet doing sub MOA is revolutionary in and of itself.

Well, 2027 here I come. Looks like that's the earliest we could potentially see some at market price.

Ceramic plates? No it wont punch through those, which is why I specified AR500 steel armor and is what is accessible to most of the world either as body armor or bolted on to technicals or VBIEDs by the Jihadi Design Bureau. But yes you are correct, it mainly punches through metal barriers much better than green tip.

Improved terminal ballistics is a huge part of why this round is so successful. It does not require yaw or "tumbling" for its terminal effects which is why it can still fragment hundreds of yards from the muzzle.

Kevlar? Anything pushed at rifle velocities will go through soft body armor.

[okie]

Ceramic plates? No it wont punch through those, which is why I specified AR500 steel armor and is what is accessible to most of the world either as body armor or bolted on to technicals or VBIEDs by the Jihadi Design Bureau. But yes you are correct, it mainly punches through metal barriers much better than green tip.

Improved terminal ballistics is a huge part of why this round is so successful. It does not require yaw or "tumbling" for its terminal effects which is why it can still fragment hundreds of yards from the muzzle.

Kevlar? Anything pushed at rifle velocities will go through soft body armor.

Depends on range. People discount soft armor, but it works extremely well at long range. Kevlar helmets have saved many lives.

[Glock9mm1990]

ITAR isn't a problem for friendly nations selling each other arms. If you think ITAR applies to them then you're missing the point. And if you think restricting M855A1 to civilians has anything whatsoever to do with security you're either delusional or just refusing to see the forest for the trees.

The purpose of the 2nd Amendment, the only purpose, is to ensure that the government doesn't restrict civilian access to arms that it has. The whole idea is to make sure the people have the same arms as they do.

Also, the government doesn't own its patents, the American people do. The government is merely a custodian of them, and has an obligation to leverage them to the peoples' advantage. That's why I said I'm fine with them getting royalties.



The problem with M193 is that it's very dependent on barrel length and twist rate. It works best out of a 20" 1:12, and the further you deviate from that the less effective it becomes. It's also limited because of its light weight and low BC. And it's a bad penetrator, so auto glass and steel is definitely a problem.

Essentially, M855A1 gives you M193 level performance, but it's not confined to certain barrels or ranges. It works out of 10-20" barrels with any twist rate and will still tumble and fragment at any point in its effective range. And all that with match level accuracy and near AP level penetration. The stuff is truly awesome, and there's absolutely nothing on the commercial market that even begins to approach it, at least not that I'm aware of. Especially for the price.

Actually twist rate doesn’t matter and has no effect on terminal ballistics regardless if it is a 1:12, 1:9, or 1:7 assuming the barrel length is the same. As long as you’re above 2600 fps you should get some fragmentation with M193.

I do agree that M855A1 is vastly superior to both M193/M855 it’s just unfortunate that it isn’t commercially available. I’ll just have to settle for 77gr SMK/TMK, speer gold dot/fusion or 50gr TSX my self.

[okie]

Actually twist rate doesn’t matter and has no effect on terminal ballistics regardless if it is a 1:12, 1:9, or 1:7 assuming the barrel length is the same. As long as you’re above 2600 fps you should get some fragmentation with M193.

I do agree that M855A1 is vastly superior to both M193/M855 it’s just unfortunate that it isn’t commercially available. I’ll just have to settle for 77gr SMK/TMK, speer gold dot/fusion or 50gr TSX my self.

Ball ammo is very much affected by twist rate. The length of the neck and how dramatically it yaws are dependent on the angle at which it enters the target. So within reason, more wobble in flight is going to give more consistent results. Less wobble means more of a chance it will impact straight on, which is going to give you a longer neck and less yaw inside the target.

[Glock9mm1990]

Ball ammo is very much affected by twist rate. The length of the neck and how dramatically it yaws are dependent on the angle at which it enters the target. So within reason, more wobble in flight is going to give more consistent results. Less wobble means more of a chance it will impact straight on, which is going to give you a longer neck and less yaw inside the target.

The U.S. Army Wound Ballistic Research Laboratory conducted terminal performance testing using 5.56 mm 55 gr M193 FMJ ammunition fired in 20” barrels of 1/14, 1/12, 1/9, and 1/7 twist rates. No difference in terminal performance was noted between shots made with the different twists. Similar testing was conducted with 5.56 mm 62 gr M855 FMJ ammunition fired in 1/9 and 1/7 twist barrels. Again, no difference in terminal performance was noted. There are some projectiles where the terminal performance can be effected by twist rate, but these are not generally in military use. Also, if the bullet is not adequately stabilized in flight, then alterations in the wound profile will be evident.

Twist rate can definitely effect external ballistics. For example, in testing ammunition at the CHP Academy in the mid 1990’s, a number of lightweight, thin-jacketed, relatively high velocity .223 varmint loads were observed to disintegrate in mid-air a few yards from the muzzle when fired from fast 1/7 twist weapons, but not in slower twists; the Federal 40 gr Blitz loading was particularly problematic in this regard. Likewise, long 70+ gr projectiles don't always stabilize in 1/9 or slower twist barrels.

[vicious_cb]

Ball ammo is very much affected by twist rate. The length of the neck and how dramatically it yaws are dependent on the angle at which it enters the target. So within reason, more wobble in flight is going to give more consistent results. Less wobble means more of a chance it will impact straight on, which is going to give you a longer neck and less yaw inside the target.

Glock is correct, its been tested. Shooting the M193 out of different twist rates makes no difference in terminal ballistics. You might be thinking of fleet yaw or angle of attack which greatly depends on the characteristics of the barrel.

[okie]

Glock is correct, its been tested. Shooting the M193 out of different twist rates makes no difference in terminal ballistics. You might be thinking of fleet yaw or angle of attack which greatly depends on the characteristics of the barrel.

The only specific testing I know about is a police department that was using A1s back in the 90's, and they refused to upgrade to rifles with a faster twist rate because it was overstabilizing their bullets and causing ice picking. I'm honestly not sure what was available back then in terms of .223 defensive ammo. I'm guessing they didn't have much to choose from, and I think they were using M193.

[Glock9mm1990]

The only specific testing I know about is a police department that was using A1s back in the 90's, and they refused to upgrade to rifles with a faster twist rate because it was overstabilizing their bullets and causing ice picking. I'm honestly not sure what was available back then in terms of .223 defensive ammo. I'm guessing they didn't have much to choose from, and I think they were using M193.

That’s because M193 can be inconsistent, sometimes it will frag sometimes it can ice pick. Twist rate has nothing to do with it however.

[okie]

That’s because M193 can be inconsistent, sometimes it will frag sometimes it can ice pick. Twist rate has nothing to do with it however.

I'm having trouble wrapping my head around that one. In any case, I think we can safely say that M855A1 makes such concerns completely moot.