View Full Version : Terminal ballistics-wise: Mk318 or M855A1?
In keeping with the theme of this forum, I ask that question. When it hits a two-legged critter, which performs better and more consistently? Let's say for a military force, not Joe Civvie.
Sure, M855A1 has some pressure issues which could make one default to Mk318, but if by some miracle increased wear on the weapon wasn't an issue, which one? Not talking barrier penetration, but I guess that should be included in the discussion.
vicious_cb
05-01-19, 18:44
In keeping with the theme of this forum, I ask that question. When it hits a two-legged critter, which performs better and more consistently? Let's say for a military force, not Joe Civvie.
Sure, M855A1 has some pressure issues which could make one default to Mk318, but if by some miracle increased wear on the weapon wasn't an issue, which one? Not talking barrier penetration, but I guess that should be included in the discussion.
1st of all M855A1 doesnt have increased wear anymore since they dropped the pressures. Both anecdotally and looking at ballistics gel, M855A1 seems to be the superior bullet. They are very close in performance but when the distances increase and velocity falls off, M855A1 looks to have a lower velocity threshold for fragmentation.
1st of all M855A1 doesnt have increased wear anymore since they dropped the pressures. Both anecdotally and looking at ballistics gel, M855A1 seems to be the superior bullet. They are very close in performance but when the distances increase and velocity falls off, M855A1 looks to have a lower velocity threshold for fragmentation.
I didn’t know that they did drop the pressure. I assume 855A1 is better at penetrating armor, I know it performed well there but I don’t know about 318 in that regard.
Sent from my iPhone using Tapatalk
A1 is running functionally the same as legacy 855 pressure wise.
A1 has a lower threshold of fragmentation
A1 penetrates hard homogeneous targets much better
I have personally found mk318 to be much more accurate. YMMV by lot number and barrel.
A1 is running functionally the same as legacy 855 pressure wise.
A1 has a lower threshold of fragmentation
A1 penetrates hard homogeneous targets much better
I have personally found mk318 to be much more accurate. YMMV by lot number and barrel.
Any idea when this pressure reduction from the original loading took place? I have heard about it but never saw something specific like "After 20XX M855A1 underwent a change where the pressure was decreased slightly".
I know nothing about the pressure, but I have noted A1 to have higher velocities than greentip, along with slightly more recoil. Maybe I’ve only used older lots?
I know nothing about the pressure, but I have noted A1 to have higher velocities than greentip, along with slightly more recoil. Maybe I’ve only used older lots?
While I am far from an expert on ammunition development and procurement, I believe one of the goals of M855A1 was rifle ballistics from a carbine barrel. Of course, given current powder technology, the only way to achieve that goal is to crank up the pressure.
Any idea when this pressure reduction from the original loading took place? I have heard about it but never saw something specific like "After 20XX M855A1 underwent a change where the pressure was decreased slightly".
M855A1 was getting tweaked so often it's hard to say, but at least 2 years ago.
M855A1 was getting tweaked so often it's hard to say, but at least 2 years ago.
Do you happen to have a link I can read on the subject? I'd be interested to see changes and timeframes.
I don't recall where I read it but supposedly the pressures weren't dropped all the way back to "regular" 5.56 NATO, but nonetheless lower than the original recipe.
kaltesherz
05-06-19, 23:06
Pretty sure the pressure reduction wasn't long after it was introduced after all the reports of breaking bolts and wearing out barrels quickly. All the lots we've been shooting are older (2014ish) and don't seem noticeably hotter than M855.
M855A1 fragments much further out than green tip, I haven't seen any hard data but from unofficial experiments people have been making with gel I wouldn't be surprised if it was past 300m. It's a huge improvement.
I don’t know when the stuff I shot was made, but the ballistics were noticeably different. POI was significantly higher, I assumed due to the increased velocity.
Sent from my iPhone using Tapatalk
davidjinks
05-09-19, 22:06
Pressures have been dropped but there are still issues with the M855A1 damaging weapons.
In regards to terminal ballistics, M855A1 is superior to the MK318. Better penetration, and fragmentation.
1st of all M855A1 doesnt have increased wear anymore since they dropped the pressures. Both anecdotally and looking at ballistics gel, M855A1 seems to be the superior bullet. They are very close in performance but when the distances increase and velocity falls off, M855A1 looks to have a lower velocity threshold for fragmentation.
Do you happen to have a link I can read on the subject? I'd be interested to see changes and timeframes.
I don't recall where I read it but supposedly the pressures weren't dropped all the way back to "regular" 5.56 NATO, but nonetheless lower than the original recipe.
Noone really knows. It was rapidly evolving in real-time, with multiple lots/charges in circulation at the same time, etc.
Pressures have been dropped but there are still issues with the M855A1 damaging weapons.
In regards to terminal ballistics, M855A1 is superior to the MK318. Better penetration, and fragmentation.
I'm just recalling this off the top of my head but the originals exceeded 60,000 PSI and now they're down to like 56,000, correct? Don't recall where I read it. So less than the original but still higher than NATO specs.
Pretty sure the pressure reduction wasn't long after it was introduced after all the reports of breaking bolts and wearing out barrels quickly. All the lots we've been shooting are older (2014ish) and don't seem noticeably hotter than M855.
M855A1 fragments much further out than green tip, I haven't seen any hard data but from unofficial experiments people have been making with gel I wouldn't be surprised if it was past 300m. It's a huge improvement.
Its target was 600m initial, but I believe they backed off to 450-500 or something as a more realistic goal with pressure reduction.
I'm just recalling this off the top of my head but the originals exceeded 60,000 PSI and now they're down to like 56,000, correct? Don't recall where I read it. So less than the original but still higher than NATO specs.
They're a few hundred PSI lower than greentip, I believe.
davidjinks
05-10-19, 12:42
It’s not so much the pressure anymore, it’s the design of the projectile. Combating the that specific issue is why the .Mil has been updating magazines. However, that’s not the end all be all answer to the issues.
I'm just recalling this off the top of my head but the originals exceeded 60,000 PSI and now they're down to like 56,000, correct? Don't recall where I read it. So less than the original but still higher than NATO specs.
PSI still high. cartage DOES NOT meet NATO/STANAG specs
ColtSeavers
07-22-20, 21:26
PSI still high. cartage DOES NOT meet NATO/STANAG specs
My understanding after reading about this round off and on for some time now is that the pressure was dropped rather quickly due to burning out barrels, which was a point the Marines use to fight acceptance, and the only problem it has with current magazines is the tip is not presented quite high enough to not gouge the feed ramps of the barrel extension a bit.
My understanding after reading about this round off and on for some time now is that the pressure was dropped rather quickly due to burning out barrels, which was a point the Marines use to fight acceptance, and the only problem it has with current magazines is the tip is not presented quite high enough to not gouge the feed ramps of the barrel extension a bit.
Even that was recanted. It started as a thread on Lightfighter from one guy with a specific issue, someone in the Army got a hold of it and took it way out of context and it blew up into something it wasn't. I'd fully accepted all of the reported issues about damaging the barrel extensions and/or feedramps until I was pointed to that thread and the OP saying that it never should've been presented that way.
M855A1 pressure and velocity have been dialed back, yet was still within the 62,000 cup specified to meet both US performance and acceptance specifications and NATO Standardization Agreements. At its hottest it was 120 fps faster than M855.
There are many, many web sites that use a photo showing an M4 barrel extension with old typewriter white-out applied for contrast showing "Chewed up" feed ramps. As stated above, this was a photo used in a powerpoint that was co-opted to show the ammo as being dangerous to issue (and total bullshit) because it "Physically damages the weapon."
The new enhanced magazine simply has a Magpul follower with a slightly elevated bullet nose presentation angle for a higher straight-in feed rather than initially contacting lower on the feed ramp. They have a brown cerakote finish on the outside mag body.
I have coached combat shooting teams and initial/basic rifle marksmanship training the last five years shooting M16A2s, M16A4s, and M4A1s (with both the old barrel taper and the Modification Work Order / new SOCOM heavy profile) and can reasonably say the M855A1 ammo shoots straighter and tighter to 500 yards than M855, and doesn't seem to be any better or worse for wear than the old ammo.
Given the choice I'd rather shoot the new ammo than M855 or M193. I have no experience with the new MK318.
69, 73, and 77 grain match ammo is for different purposes than mass-issue ammo for line Joes.
Ned Christiansen
07-23-20, 10:36
I would also be very interested to see any good documentation on taking the edge off of M855A1. AND any kind of study or credible evidence of it chewing up feedramps. I have always suspected that one pic that was so blurry and oddly showed damage only on one side. If feedramp / barrel extension damage is a real thing it seems like there wold be a lot of more believable pics out there. I'm not saying "it can't be true", I just want real pics and data if it is. My limited experience with the A1 is that on the terminal ballistics side it does several things well. "Match accurate" it has not been for me.
ColtSeavers
07-23-20, 17:01
Thank you all for the clarification. I have only half heartidly kept up with m855a1 and apologize if I came across as trying to continue to spread BS.
Thank you all for the clarification. I have only half heartidly kept up with m855a1 and apologize if I came across as trying to continue to spread BS.
I didn't take it that way, I was just part of the problem at one point so trying to correct that.
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.