.223 Penetration

[Nightcrawler]

Okay, I see a certain contradiction in the supposed performance of .223/5.56mm FMJ ammunition.

All the AR makers these days say that .223 FMJ will fragment and penetrate less than a pistol round, except in body armor, in which it apparently doesn't fragment.

They say fragmentation happens in multiple layers of obstruction. This apparently does not apply to steel; I've shot .223 FMJ ammo through an old steel pot helmet, a 55 gallon drum, etc. It went in on the near side and out on the far side without slowing down much.

A .45ACP pistol round and a .357 Magnum round (from a 16" barrel) did not exit out the far side of the helmet, in my own little tests. .223 and 7.62x39mm both went clean through.

Now, I'm willing to bet that drywall makes for poorer armor than steel. I've also seen AR advocates claim that SS109 rounds will penetrate a kevlar helmet at 1100m, and that they'll out-penetrate .308 FMJ.

And this is all with FMJ ammo.

Here's what I don't understand. In my OWN OBSERVATIONS, .223 did NOT fragment all of the time. In fact, it stands to reason that hardball ammunition, not designed to fragment, would NOT RELIABLY FRAGMENT.

Nevertheless, I'm assuming fragmentation is the key. Otherwise, it makes no sense. How else could a rifle round moving at 3100 feet per second penetrate less than a pistol round chugging along at 900fps?

So what's the REAL story? I've read the reports of the FBI tests on Olympic's page. On the other hand, the tests done by High Road/TFL members I've read do not seem to substantiate the claims of the FBI.

I'm really confused on this.

 

[Matt G]

I'll do some digging, but there was a DOJ study, I think, and I know I read a fascinating article in one of the gun rags (Guns & Ammo, I think it was) about this. It seems that, when comparing fmj to fmj, the velocity is the undoing to the .223 round, even in something as relatively soft as sheetrock.

I too have done some tests with very heavy HP 8" glycol pipe that was about 3/8" thick. No pistol round out there would penetrate nor even put a dent in this stuff, yet center hits with .223 just bore right on through. The thing is, steel is HARD. The inertia of the big bullet simply won't let it through. But push the velocities up to 3k or so, and sheetrock will cause little lead-core 55 g bullets to tumble and break up... usually. Once they're lost their aspect orientation to the rifling, and have broken up, it's fairly easy to see how they would be slowed and stopped or at least would do far less damage. I think the medium is very important.

 

[Bartholomew Roberts]

A few things you need to remember - the fragmentation doesn't apply equally to all 5.56mm rounds. FMJ rounds like Wolf and S&B will not fragment because the bullet has a thicker and tougher jacket. Even rounds that do exhibit this may not always do it reliably - military FMJ fails to yaw about 15% of the time and M855 may not yaw at all from lot to lot due to all the different variables effected by its more complex bullet construction.

Military FMJ rounds like M193 (55gr) and M855 (SS109/62gr) will fragment because their jackets are thinner to start with and they are weaker from the cannelure (used by the military to prevent setback) as well.

Also, understand that the process isn't instantaneous. The round hits a medium and travels for some distance in the medium - outside of air, the natural way the bullet wants to travel is base end first so as the bullet moves through a solid or liquid medium for several inches, it wants to flip itself to that orientation.

The problem is a thin-jacketed 5.56mm traveling at around 3000fps can't handle the stress of this flip while traveling through a solid or liquid medium at the same time - it breaks apart and fragments.

On your steel pot or your steel drum, the round doesn't have time to yaw, let alone to fragment inside the steel. At longer ranges/lower velocities the bullet isn't going fast enough to break up and remains intact.

Check out this FAQ:
http://www.ammo-oracle.com/

Also, try your experiment again but with a thicker barrier and make sure the ammo you are using is one of the types of 5.56mm FMJ ammo that fragments - a lot of these types of ammo don't and will put nice holes in all sorts of barriers and keep right on going.

Also, remember that the tests don't say that 5.56mm is a magic round - just that it has less potential to wound or kill after passing through intermediate barriers - you might still get impressive holes through both sides of your barrier; but if it fragments on or before exiting, those fragments will have a lot less wounding potential than a solid bullet.

 

[Johnny Guest]

One other consideration re: .223/5.56 mm ammo- - -

Most discussion tends to center around FMJ bullets--Lighter, heavier, thick jacket vs. thin, etc.

For home defense and/or law enforcement, the bullet of choice is the 50 to 55 gr. SP or HP. Yeah, I know, not as accurate at long ranges as the heavier bullets. So what? It takes bench resting with an accurate rifle/sight combo to tell the difference at 100 yards, much less fifty feet!

A 52 gr. HP or 55 gr. SP at 2900 will bust up on a sheet rock wall far quicker than an FMJ of any description. So long as the trajectory is similar, FMJ is fine for practice and qualifications, saving the nifty varmint loads for a crisis situation.

Best,
Johnny

 

[Erich]

Here's an article by Gunsite staff discussing penetration characteristics of .223 rounds, put up by our friends at the Maryland AR15 Shooters' Site.

http://groups.msn.com/TheMarylandAR15ShootersSite/223penetrationtest.msnw

 

[Navy joe]

Several things. First in most of our modern toys the std 55gr we buy everywhere is massively over-stabilized by the 1-7 and 1-9 bbls.

Assume everything is going out the back. We've been led to think that a bullet coming out of someone's body is bad, but the more holes to bleed out of the merrier. Just be aware of what is beyond your target even with a .22 short.

Try Win CXP1 40gr hp or some blitzkings or something, bet they will fragment. I keep a mag of them for the populated area I live in.

 

[Poodleshooter]

Awhile back I posted some support for the heavier 64gr softpoint deer hunting .223 ammo on the ar15.com board. That caused a fun poopstorm of a topic in the ammo forum. They may not fragment as powerfully as the M193, but they expand reliably in many different mediums, and they retain expansion at ranges well beyond the M193 fragmentation threshold.