55 gr vs. 6n gr

Pinecone said:

M855 was designed to penetrate a ballistic helmet at longer range.

Unfortunately, it is a very stable round, so sometimes, when it hits the target, it drills right through, leaving a .223" hole. M193 (55 grain) and M262 (77 grain) are much less stable, so when entering the target, they "exhibit excessive yaw deviation." Which means they tumble and fragment. So better performance on soft targets.

The military is going to the M855A1, which is much improved soft target performance. This is not available to the public.

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I do wonder if it ever will be. I kind of suspect no, but I also don't know that it would technically be AP under current ATF regulations. I am sure it is one of those where they are cranking out as many for the military as they can and don't see a current market for what is probably $1+ per bullet ammo on the civilian market. Well, not when their production is tied up.

lazarus said:

I do wonder if it ever will be. I kind of suspect no, but I also don't know that it would technically be AP under current ATF regulations. I am sure it is one of those where they are cranking out as many for the military as they can and don't see a current market for what is probably $1+ per bullet ammo on the civilian market. Well, not when their production is tied up.

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It's not AP per current Federal law. All production is dedicated for US Mil. That said it's earning a reputation for shitty long term (not long range) performance, cracking bolts and barrel lugs, increased wear and tear as its essentially a 5.56+p round. Not a problem for Big Army with thousands of armorers and millions of replacement parts but definitely an issue for the citizen and/or LE in smaller departments.
There's plenty of market for a $1 a round performance round as Mk. 262, Hornady Superformance, Hornady TAP and Speer Gold Dot all hover in that same price range. I wouldn't buy it but some idiot will to have the latest in mil spec.
I'll stick with Federal Fusion, Mk. 318 and Mk. 262.

Pinecone said:

so sometimes, when it hits the target, it drills right through, leaving a .223" hole.

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This is only a symptom of firing the round out of a weapon system it wasn't designed for.

It's not a "stable" round, as it is allowed very poor tolerances and is acceptable up to 7MOA of deviation. At 100 yards, that's a 7" spread.

The problem is that the round is heavily dependent on proper external ballistics to have the correct wound ballistics it was designed to exhibit.

Stability is not the issue. M193 is a 4MOA round and 262 even tighter. Bullet design and proper usage is the issue.

mopar92 said:

It's not AP per current Federal law.

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Federal law on "what is AP" is a joke, because virtually any round with enough velocity will poke right through everything but STPs. M193 zips right through many armors.

That is the milspec complete cartridge and bullet for the m855a1. Sure some of it is the increased pressures and resultant velocity which aids its penetration, but a civilian version chambered at closer to SAMI specs likely wouldn't be nearly so high wear and also be better than m855.

On the accuracy of m855...sure it CAN be 7MOA and be accepted. It typically is massively better than that. I still haven't taken my AR-15 to the range yet, but I see most m855 and m193 coming in pretty close to each other, 2-3moa with the m193 being only slightly better on average. Based on anecdotal reports and reviews of different manufacturers ammo.

To expand, with m855 like chamber pressures and velocity the m855a1 would still be a lot better at things like cinderblock penetration. There the m855 may have enough energy to penetrate completely through, but cinderblock is so hard it breaks up the round. Something that can hold together a lot better like the m855a1 may penetrate throigh even without the extra velocity. Speculation of course.

Seems like the m80a1 absolutely could though.

lazarus said:

To expand, with m855 like chamber pressures and velocity the m855a1 would still be a lot better at things like cinderblock penetration. There the m855 may have enough energy to penetrate completely through, but cinderblock is so hard it breaks up the round. Something that can hold together a lot better like the m855a1 may penetrate throigh even without the extra velocity. Speculation of course.

Seems like the m80a1 absolutely could though.

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The composition of the 855a1 projectile is completely different than that of the 855. It has nothing to do with the "hardness" of the bullet. The tip of 855 is a copper jacket, the tip of 855a1 is exposed steel. It is apples to oranges.

lazarus said:

That is the milspec complete cartridge and bullet for the m855a1. Sure some of it is the increased pressures and resultant velocity which aids its penetration, but a civilian version chambered at closer to SAMI specs likely wouldn't be nearly so high wear and also be better than m855.

On the accuracy of m855...sure it CAN be 7MOA and be accepted. It typically is massively better than that. I still haven't taken my AR-15 to the range yet, but I see most m855 and m193 coming in pretty close to each other, 2-3moa with the m193 being only slightly better on average. Based on anecdotal reports and reviews of different manufacturers ammo.

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855a1 is still within SAAMI spec. At max the pressure is 61,000. 5.56 max is 62,000.

The purpose of my bringing up the accepted tolerances is to debunk the whole "stability" myth. Yes, generally it will be tighter, but that still has zero effect on wound ballistics. It's one of the many myths about firearms that will takes decades to shake.

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There is a difference between ballistic stability in air and in flesh however. The heavier rear of the m855 does provide a tendency to tumble compared to the m193 which is more nose heavy. However until longer range the m193 has much higher velocity which dramatically increases the pressure on the front of the bullet. If they were both traveling the same velocity the m855 likely would be more likely to tumble.

As for hardness, it isn't apples to oranges. The m855a1 is harder than the m855 for the overall frontal section. This is why it can penetrate cinderblock at short ranges where the m855 breaks up. Cinderblock is extremely hard, which fractures the tip of the m855 (and m193 just flattens and breaks up). Same reason m855 against very hard armor penetrates worse than m193, there velocity has a lot more to do with it and something like AR650 is massively harder than the AR375-450 tip of the m855. At least till you get up on a couple of hundred yards. There the m855 is carrying more velocity and a lot more energy.

Against soft materials the m855 has slightly better close range penetration, but it is extremely close. At medium and long range there is no comparison.

lazarus said:

There is a difference between ballistic stability in air and in flesh however. The heavier rear of the m855 does provide a tendency to tumble compared to the m193 which is more nose heavy. However until longer range the m193 has much higher velocity which dramatically increases the pressure on the front of the bullet. If they were both traveling the same velocity the m855 likely would be more likely to tumble.

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Nowhere in the science of ballistics does the term "tumble" exist. External ballistics, terminal ballistics and wound ballistics are all separate. You've been provided poor information both on "tumbling" and the nonsense about the projectile balance (look at a cross-section of m193, where the lead slug is located [most of the weight] and even the small air gap between the nose of the slug and the jacket) and velocity-induced pressure.

m855 REQUIRES speed to be able to do its job, which is to yaw and flip rear first (not tumble) and fragment. m193 will do its job of penetrating and the jacket providing some degree of fragmentation regardless of changes in velocity from barrel length.

If you fired both from a 14.5" barrel, the m193 would function correctly while the m855 would result in what many experience where it just pokes a clean hole. It needs the velocity to yaw, and out of a sub-20" weapon system it simply does not have it.

lazarus said:

As for hardness, it isn't apples to oranges. The m855a1 is harder than the m855 for the overall frontal section. This is why it can penetrate cinderblock at short ranges where the m855 breaks up. Cinderblock is extremely hard, which fractures the tip of the m855 (and m193 just flattens and breaks up). Same reason m855 against very hard armor penetrates worse than m193, there velocity has a lot more to do with it and something like AR650 is massively harder than the AR375-450 tip of the m855. At least till you get up on a couple of hundred yards. There the m855 is carrying more velocity and a lot more energy.

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It is apples to oranges, because they are two wildly different types of bullet composition. m855 is fully copper jacketed with a lead slug behind the penetrator whose components are not bound together. m855a1 has its penetrator exposed and its copper slug is cannelured to the penetrator, with a copper jacket only going to the base of the penetrator. m855a1 is a considerably stronger construction.

Do you know what else is hard? Ceramic armor plates, which M193 can poke right through. If you're wanting to talk armor penetration, you may as well use a real-world scenario.

As for the external ballistics you mentioned, I'm somewhat baffled... How do you figure that two projectiles of the same weight, with one (a1) having a higher BC and muzzle velocity is somehow ballistically inferior to the other. 855 has more drop of elevation and speed than 855a1. You may want to check your googles, because even the Army disagrees with your statement; regardless of barrel length.

lazarus said:

Against soft materials the m855 has slightly better close range penetration, but it is extremely close. At medium and long range there is no comparison.

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This is simply not true. As has been seen in the Middle East, in many cases m855 would not yaw within 7" of tissue before exiting the other side of the body type commonly seen in the local population. 855a1 on the other hand would yaw, up to and including separation of the penetrator from the slug.

I didn't say, or at least I didn't think I said that the m855 was ballistically superior to the m855a1 for either BC or stability.

Both the m193 and m855 are dependent on velocity to tumble. The m193 starts off at a higher velocity and also has a higher velocity with shorter barrels.

If armor is hard enough to cause the projectile to break-up, then velocity and a lesser extent overall energy determines penetration. Ceramic armor and the harder steel hardened armors are harder enough that they'll compromise the m855 and the m193, so the velocity advantage of the m193 makes it superior at short range to the m855.

Cinderblock is not hard enough for that to be true.

It's the reason steel is hardened and the reason why older projectiles circa WWII used ballistic caps to prevent the projectile from being broken up, they mushed and cushioned the projectile allowing to to slam mostly whole in to the armor. If the armor is sufficiently hard enough still it would shatter the projectile and then it was limited to velocity and energy on it it could damage or penetrate the armor. If the projectile is harder than the armor, or at least very close it generally won't shatter on the armor, and will have a penetration advantage as it'll have a smaller contact patch as it doesn't deform and transfer the energy over a larger area.

The m855a1, other than wear on the weapon, is superior in every way to the m855. The m193 is better at short range for almost everything over the m855, except masonry and soft metal...though not much difference and at medium and long range the m855 (if it hits) can be superior. Can be.

lazarus said:

I didn't say, or at least I didn't think I said that the m855 was ballistically superior to the m855a1 for either BC or stability.

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Let me help you remember:

lazarus said:

At least till you get up on a couple of hundred yards. There the m855 is carrying more velocity and a lot more energy.

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That statement highlights your lack of knowledge on the topic, both in regards to the ammunition being discussed and ballistics as a whole.

lazarus said:

Both the m193 and m855 are dependent on velocity to tumble. The m193 starts off at a higher velocity and also has a higher velocity with shorter barrels.

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Can you please show me where "tumble" exists in the science of ballistics? Seriously. Reputable scientific source.

lazarus said:

If armor is hard enough to cause the projectile to break-up, then velocity and a lesser extent overall energy determines penetration. Ceramic armor and the harder steel hardened armors are harder enough that they'll compromise the m855 and the m193, so the velocity advantage of the m193 makes it superior at short range to the m855.

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Velocity and energy... the two most poorly understood factors in terminal and wound ballistics.

Please explain why STPs (Special Threat Plates) exist above and beyond standard ceramic and composite armors for 193 and 855...

Can you quantify your superior statement?

lazarus said:

The m855a1, other than wear on the weapon, is superior in every way to the m855. The m193 is better at short range for almost everything over the m855, except masonry and soft metal...

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Do you understand how it causes wear on the weapon? Earlier you posted a thread about the gas block being misaligned after you installed it, curious as to whether it mattered.

Well, it definitely matters for the proper regulation of gases into the operating system. You probably also had no idea as to what the gas port diameter is on the barrel you purchased, and how that also affects the operation and resulting wear. (It varies widely both in design and QC)

m855a1 causes gas port erosion, which gives the system too much gas and starts wearing everything. The reason it is higher pressured is that the bullet has to be longer to maintain the same weight and as close of a ballistic profile as 855 as possible. So to keep the same ammunition length, it's seated deeper, raising pressure. They kept that pressure intentionally, because it addresses the fact that it would be used in shorter-barreled systems than what 855 was designed for. It is not a flaw, as has been pointed out previously in this thread regarding Big Army's logistics.

lazarus said:

though not much difference and at medium and long range the m855 (if it hits) can be superior. Can be.

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Again with this, and I even provided you with a basic ballistic trajectory chart showing you how 855a1 has less drop (thanks to a higher BC and MV) than 855. Short of bending the laws of physics, there is absolutely no way that 855 is "superior". Which again, I'll ask you to quantify your statement.

You're out of your lane. Quit trying to be correct by posting derp and learn something.

Your first quote I mangled the heck out of it. I meant at up to a couple of hundred yards the m193 has higher velocity which aids in its penetration against hard targets. Beyond that the m855 is faster and by that point carries a lot more energy because of the highs BC. There wasn't a comparison of the m855 to m855a1 near there at all.

If you read my statements several times I have NOT said the m855 is superior to the m855a1. I HAVE said the m855 is superior to the m193 for penetrating hard targets at medium and long range and soft targets at short range as well as select types of hard targets at short ranges. Penetrate, not soft target wounding. Just so I am clear. The m855a1 causes more wear...I haven't disputed that.

For the misaligned gas block, I've now checked the alignment and it is dead on. My eyes must be twisted. For hole size, no I didn't measure it exactly. A little less than .1"? And yes I understand exactly what the relation is on how the port and gas block interact to feed the BCG. I was asking...because you know, the gas block itself is oversized compared to the gas port, so alignment doesn't need to be exact. I was asking if anyone knew by how much it could be off as I didn't want to dig up calipers to measure both and then try to measure the angle the gas block was off.

For terminal stability, that is dependent upon spin rate, pressure and center of gravity. The higher the spin rate. M193 and m855 have a center of gravity far enough back that the slower they spin and the higher the pressure that is exerted upon them, the more apt they are to tumble. It is velocity dependent. The primary wounding factor is fragmenting at the cannular of the round. The m855 has a center of gravity further back on the round due to its construction, but it is also traveling a fair amount slower. I haven't taken any classes on bullet ballistics but I have taken a few classes on aerospace engineering. The CoG/pressure thing is the same reason a rifles slug is shaped like a shuttle cock to balance it with a CoG very far forward. Also why bullets when they go subsonic tend to lose accuracy as they become upset as they pass the supersonic barrier on the way back down as bullets have a CoG behind their midline. The process of going subsonic causes a big pressure jump going subsonic from transonic. Also why non deforming bullets tend to tumble, because they have CoG further back. Boat tail bullets actually tend to have higher terminal stability and pistol bullets because they are stubby tend to be more stable.

MontaniSemperLiberi said:

This is only a symptom of firing the round out of a weapon system it wasn't designed for.

It's not a "stable" round, as it is allowed very poor tolerances and is acceptable up to 7MOA of deviation. At 100 yards, that's a 7" spread.

The problem is that the round is heavily dependent on proper external ballistics to have the correct wound ballistics it was designed to exhibit.

Stability is not the issue. M193 is a 4MOA round and 262 even tighter. Bullet design and proper usage is the issue.

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Not according the former head of Lake City ammunition plant.

The reason it does not yaw upon penetration is due to excess stability.

If it were unstable, it would yaw.

Exterior ballistics accuracy and terminal ballistics stability are NOT the same thing.