I'm not sure if this is the right forum section for this, but has anyone tested the penetrative capabilities of Hornady's A-Tip bullets compared to M855? What benefit or detriment does the aluminum tip have if any, in this way? Is it softer than what's in the M855?

A-tips expand and aren’t known for penetration. M855 isn’t the best penetrator either.

The basic spec for the 855 bullet calls for a steel insert, which should keep the nose of the bullet from collapsing when it penetrates that "3mm mild steel plate at 600M" in the spec.  While you'll see the steel insert called a "penetrator," it is NOT the same thing as the hardened steel or tungsten penetrator in actual armor piercing bullets.

M193 bullets CAN penetrate that 3mm mild steel plate at 600M, but only if they strike mostly nose first, so the real reason for a steel insert in the original SS109 bullet was to shift the center of mass of the bullet toward the base.  This changes a lot of dynamics, primarily it keeps the SS109 pointing more nose first for a longer distance, with a higher likelihood of impacting nose first.

SOME countries use a hardened insert.  As far as I know, that's not part of the M855 or 5.56mm NATO requirement.

Anyway, unless you're concerned about penetration at really extended ranges, Hornady makes MUCH better bullets than any M855 bullet.  The steel insert creates a variable in bullet construction that makes the M855 bullet less consistent in several ways, particularly in its weight distribution axially; it may stay nose-first for a longer distance, but it may yaw away from point of aim in random directions.  And of course the spec for M855 accuracy is about 1MOA (more or less) anyway.

So, without having any personal experience with the Hornady A-Tip bullet, I'd still go with it over the historically less accurate M855 bullet.

Easy win for M855 as Hornady does not make a A-tip (aluminum tip) bullet for 5.56/.223  

There is a 90 grain 22 cal bullet but it is almost certainly meant for .224 Valkyrie. It is most likely too long for 5.56

They do have the ELD Match bullet in 73gn for 5.56. This is a polymer tipped bullet.

Afaik m855 is nowhere near 1moa. More like 2-3. And more like 4-5 considering the rifles it was fielded in.


Fascinating information otherwise.

Paragraph 3.11 of MIL-C-63898 C, Accuracy:
“Both average vertical standard deviation and the average horizontal standard deviation shall be no greater than 6.8 inches at 600 yards, or alternatively, no greater than 1.8 inches at 200 yards using an indoor range.”

That works out to closer to 2+MOA.  I misremembered the spec.  Other ammunition specs call for mean radius, a value that requires far simpler (and less error-prone) calculations.  “Average horizontal and vertical standard deviation” is not even close to “mean radius”.  I don’t have time to work through how they compare, but this Ballistipedia article gives all the gory details, using math I haven’t used in a long time.

Mean radius.

Whoops, didn't read ahead.

The M855 steel penetrator is hardened to some degree.

It is medium carbon 1045 steel, hardened to 40 to 45 HRC.

That's quite a bit harder than dead soft 1045 steel and requires heat treating to get there.

It often penetrates better than lead core 7.62x51 bullets.

The M855 steel doesn't weight much, about 10 grains.

I'm not sure I agree with all of your points ...........

But that as it may.........  The OP's question was to comparing M855 to the Hornady "A-tip."  

As the other poster stated, the question is moot as there isn't a "A-tip" usable in a Standard AR (except the 90gr which as the other pointed out is probably for the 224V etc).

Hornady doesn't make mention of how the tip is constructed (if it's tempered of not) but then I don't know of any source that shows the "hardness" of the polymer tips either.  
https://www.hornady.com/bullets/a-tip-match#!/

But common sense would indicate that yes, it is softer than the steel insert of M855.    

Standard deviation… unsure what that means for extreme spread. Although it or mean radius is probably a better measure for a fighting rifle.

Also, that’s probably from a quality test barrel. A rack grade barrel will be less.

The only 22 caliber A-Tip Hornady makes is the 90 gr. It is a match bullet designed to poke holes in paper. If used in 223 Remington it needs a longer freebore and longer barrel and faster twist than is typical for ARs.

That's a totally different class of bullet than a 62 gr SS109 NATO green tip, which was designed to pop through light body armor and helmets worn by Soviet conscripts walking through Poland toward western Europe, out to the effective range of the M16.

Different rifles, different twist, different seating depth, vastly different costs, different applications.

If your budget allows for A-tips and you care about terminal ballistics, then your budget allows for much better .224 caliber bullets than either the A-tip or the SS109.

It's not standard deviation. It's average vertical standard deviation and average horizontal standard deviation.









Yes.

..

I don’t think a rifle that stacks 9 in 1/2” and throws the last 6” out would be sufficient for law enforcement sniping even if it had an excellent mean radius.

A rifle that "stacks 9 in 1/2" is not going to "throw the last 6" out".  Posts like that demonstrate your lack of knowledge and experience on the subject matter.


...

Incorrect. The cited specification of the average vertical standard deviation and the average horizontal standard deviation of “no greater than 1.8 inches at 200 yards using an indoor range” will equate to an average extreme spread of 9.048” for 10-shot groups at 200 yards, or 4.32 MOA.


...

I’ve actually seen that, from a police rifle. Turned out to be an easily correctable problem. But hey, you do you.

Sure you have, which is why what you first posted before you made your 08:44:03 edit was this . . .




...

Yes, I decided that I didn’t want to act like an ass in the tech forums like you are.

And in fact I have, back when I spent a lot of time hanging out with a buddy that fixed such problems professionally. But what’s the problem? The mean radius was in spec!

<GD post removed> dryflash3

Thanks.

Memory was rusty, but I thought I recalled milspec being ~4 MOA (also thought I recalled something about 3 x 10-shot groups to test batches), i.e. not exactly match grade, although a lot of it usually tests closer to 2-3 MOA (probably safer to make it a little better than spec than risk whole runs being rejected).

A group with nine shots in 1/2" and one out 6" would have a mean radius of something around 0.8 - 1.1 ...

An excellent mean radius is something in the 0.2x range. Something above the 0.3x range would be grossly unacceptable to anyone interested in precision.

In other words, you've proposed an hypothetical where the math doesn't remotely match reality.

You've got a very strong opinion about a technique you don't seem to understand.

Well there’s a reason it got sent to the shop. Turned out to be a threading issue.

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