5.56 for defense in short barrel

[Excalibur]

What's a good round for defensive use in a short barreled AR in 5.56? 10.5 in barrel

 

[Vigilant]

TAP SBR looks promising, or MK262

 

[turnerdye1]

My department ended up testing a couple different loads and ended up with Federal Premium 223 62gr SP. Its the LE223T3 version. Our SWAT uses 10.5" barrels and it was best at expansion, glass penetration, and sheet metal.

 

[grunt soldier]

My department also did some testing and we had very good results with the speer soft point ammo. We ended up with the 62gr LEO versiin

 

[avboiler11]

[video=youtube;31oE-_ZFJGs]https://www.youtube.com/watch?v=31oE-_ZFJGs[/video]

 

[croy]

My department ended up testing a couple different loads and ended up with Federal Premium 223 62gr SP. Its the LE223T3 version. Our SWAT uses 10.5" barrels and it was best at expansion, glass penetration, and sheet metal.

This is what I recently bought except 55 grain. Should've went with a higher grain but it'll work.

 

[NKBJ]

The regional weapons training officer that showed the better 2/3's how to handle a AR used the Nosler partition and 748.
Never ventured to question his wisdom. Well, but that was a different place, a different time.

 

[sht4brnz]

A pistol round 9mm, 10mm, 45acp.
Rifle rounds are designed to expand at rifle speeds.
The only benefit you get from an ar pistol chambered for a rifle round is capacity

 

[natdscott]

Mk 262 Mod 1 is indeed pretty nasty. Cloned it, shot it, of course found it did exactly what it should. It's a legitimate 800 yard load.

That being said, a hot load behind the 65 Sierra GameKing is absolutely hellacious, even if it doesn't look "cool"...what with that old fashioned lead soft point. That always expands. And initiates consistent jacket upset. And doesn't deflect to the degree other meplats do....

Huh. I guess I made a point there.

I don't know that glass and steel penetration is that big a thing to consider when discussing a "defense" rifle. That being said, ALL .224 pretty much suck, and shed jackets in spectacular fashion. Some...like the Fed bonded...are just less bad. I don't know about the Barnes stuff, but I don't hear of it in much use by much of anybody that uses.

sht4brnz, I'ma have to disagree with you there. Even in a 10" SBR, at short range, the AR .223 is one mean sum*****. I grant you that the rifle rounds will not be evenly mushrooming or anything when impacting at 7 feet, but from the things I've shot at close range with rifles, I can say that they are pretty devastating.

I think the 10" and 14" platforms would really begin to wane at 200 yards versus a 16" or 18" barrel, but that's not really much for discussion in a "defense" thread.

-Nate

 

[SpartanHD]

I've never really bought into the "defensive" rounds bc of their price. I know the test show more damage but I'm still in favor of using what you train with. Also, I don't know if you will get much expansion in a close quarters situation with a rifle. I may be wrong tho. Go with what you can afford and keep training with it.

 

[sht4brnz]

In this link you'll find an fbi report of a case study regarding the performance of service issue ball ammo for rifle and pistol.
I must warn it is graphic. http://www.defensivecarry.com/documents/officer.pdf

The following link is ballistic gelatin tests with pistol ammo. I cannot find one of similar substance for rifle ammo.
http://www.luckygunner.com/labs/self-defense-ammo-ballistic-tests/

Bottom line is, shot placement means more than anything.
I feel a pistol caliber carbine will offer you the advantages of a rifle for shot placement, have less likelihood of an over penetration scenario, and be more effectively suppressed (these are considerations to make if used while in your pajammas)

 

[rhino]

What's a good round for defensive use in a short barreled AR in 5.56? 10.5 in barrel

Depends on whether you're interested in maximum wounding capacity in flesh, or you need to poke through intermediate barriers.

The most effective wounding mechanism for 5.56 is when the bullet yaws upon entry into flesh, turns sideways, and hopefully fragments after sufficient penetration. M193 projectile (a specific 55gr FMJ) will do this reliably when it impacts at 2700 fps or higher (some say down to 2400 fps). The length of your barrel will determine the effective range at which your bullet will still be moving that fast on impact. A 20 inch barrel will give you more velocity, thus a longer range at which the projectile is moving at higher thand 2700 fps. A short barrel like yours will reduce the range, but I don't remember a ballpark for a distance when you'd drop below 2700 fps.

In general, with all else equal, the longer a 5.56 bullet is, the lower the speed at which it will yaw and fragment. For instance, the 68 gr OTM bullet that Black Hills uses fragments at longer distances than M193 projectiles. The bullet used in the Hornady 75 gr TAP are even better in that regard and the 77gr 5.56 as loaded by Black Hills and the equivalent are better yet.

If I were using an SBR in 5.56x45mm, I'd go with Hornady TAP 75gr or Black Hills 77 gr.

If you need better performance going through glass and other intermediate barriers, then look at the bonded jacketed soft points that others mentioned. They do well in that regard, but they don't have comparable wounding capability to rounds I mentioned previously because they rely on expansion to make a bigger hole rather than yaw and fragment. Avoid M855 (62 gr NATO ammo) -- it's notorious for shedding its jackets when passing through glass or sheet metal and what's left often has inadequate momentum to do much damage.

I would avoid lightweight varmint bullet that are designed to fragment on impact. Those are great for making prairie dogs explode and knocking chunks out of coyotes, but they may not penetrate deeply enough in a 2-legged predator to do enough damage to incapacitate. Plus they're poor performers on intermediate barriers.

 

[avboiler11]

Why the emphasis on 5.56 fragmentation velocity, when there are plenty of quality modern expanding bullets available for non-Hague users?

I've used a Mk262 clone on Kentucky deer with a Nosler 77gr CC and it left an exit wound I could easily stick my thumb into...but there was zero evidence of fragmentation on a ~65yd head shot at 2740fps from a 18" SPR that traveled about 10" through neck before exiting, although it was clearly tumbling.

Mk262 is obviously a proven combat load from Mk18s, but I do wonder if an expanding bullet would be a better mousetrap at stub-nose velocities...

 

[rhino]

Why the emphasis on 5.56 fragmentation velocity, when there are plenty of quality modern expanding bullets available for non-Hague users?

I've used a Mk262 clone on Kentucky deer with a Nosler 77gr CC and it left an exit wound I could easily stick my thumb into...but there was zero evidence of fragmentation on a ~65yd head shot at 2740fps from a 18" SPR that traveled about 10" through neck before exiting, although it was clearly tumbling.

Mk262 is obviously a proven combat load from Mk18s, but I do wonder if an expanding bullet would be a better mousetrap at stub-nose velocities...

The "tumbling" (actually yawing) is why you saw a permanent wound channel that big. A bullet traveling sideways through flesh makes a big hole, much bigger than an expanding 0.22 inch projectile can. When they fragment after sufficient penetration, the wound channel is huge.

If you find an expanding bullet that suits your needs, go for it!

 

[NKBJ]

The strength of the original design concept of the round is pretty much ignored or even considered an inconvenience. And that's a curious state of affairs.

https://www.indianagunowners.com/forums/ammunition-reloading/405570-do-you-load-tumble.html

 

[rhino]

The strength of the original design concept of the round is pretty much ignored or even considered an inconvenience. And that's a curious state of affairs.

https://www.indianagunowners.com/forums/ammunition-reloading/405570-do-you-load-tumble.html

I don't know about the original design concepts, but yaw and fragment of 5.56 projectiles isn't dependent on the stability or lack thereof while the bullet is in flight. The projectile starts to rotate and turn sideways in fluids and fluid-like media because the center of mass is biased toward the rear of the bullet. When fired from a barrel with a sufficient twist rate of rifling, the projectile is stabilized while in flight. With the exception of the necessary speed on impact, yawing and fragmenting after impact are independent of the bullet's motion prior to impact.

 

[NKBJ]

The idea was to have barely adequate stability. Close in not so much and the velocity promoted break up. Further out, more propensity to tumble and make the holes bigger. Just stuff I learned reading men's magazines in the sixties, like VC boobie trap designs and other essentials of the decade.

 

[dudley0]

I chose the Black Hills 5.56 with a 50 gr Barnes TSX. Still has good results from a 10.5" barrel. Basically barrier blind as well.

Possibly still does its job in shorter barrels, but I haven't been able to safely suppress say a 7" so I have not delved into close range ballistics from anything under the 10.5"

 

[natdscott]

I don't know about the original design concepts, but yaw and fragment of 5.56 projectiles isn't dependent on the stability or lack thereof while the bullet is in flight. The projectile starts to rotate and turn sideways in fluids and fluid-like media because the center of mass is biased toward the rear of the bullet. When fired from a barrel with a sufficient twist rate of rifling, the projectile is stabilized while in flight. With the exception of the necessary speed on impact, yawing and fragmenting after impact are independent of the bullet's motion prior to impact.

Shhhh! That's science instead of internet.

The idea was to have barely adequate stability. Close in not so much and the velocity promoted break up. Further out, more propensity to tumble and make the holes bigger. Just stuff I learned reading men's magazines in the sixties...

That may have been what the men's gun rags stated at the time, but that's not how the eventual M16A2 platform worked out. The 1:7" NATO twist is far from 'barely adequate', and is fully 100% tighter than the original XM16E1s shipped.

NO elongated bullet going through ballistic transition into as dense a medium as a human torso will remain dynamically stable through that transition. Catastrophic yaw results from over-turning moment of intertia being drastically increased on the meplat. No amount of rigidity of the rotational axis is enough to prevent this, and the ass end tries to become the front.

Solid bullets can handle it, and some heavier jackets can,..."match" bullets, by their very nature for consistency in target shooting, have thin jackets. Going into yaw, the jacket on the 77 MatchKing's long axis ('cannelured' or not) does NOT have the strength to tolerate the force imparted, and it shreds. Berger's are worse.

The lethality has ZERO percent to do with any "hollowpoint", which is why it is not applicable to Hague, or any other convention, and is in common use in combat. Same for the 175 SMK and 190 SMK in common use in the .308 and .300 WM rifles. That they shred pretty badly is not worse than some Hague-constrained 7.62x39 open-base ammunition whose bullet yaws in the same fashion, and whose jacket holds 'integrity', but crushes like a pop can and sprays lead out the bottom...

...but as avboiler questions, I ask "Why not have both?!"

65 GameKing @ 3,000.

-Nate

 

[avboiler11]

The "tumbling" (actually yawing) is why you saw a permanent wound channel that big. A bullet traveling sideways through flesh makes a big hole, much bigger than an expanding 0.22 inch projectile can. When they fragment after sufficient penetration, the wound channel is huge.

If you find an expanding bullet that suits your needs, go for it!

I suppose my point is, with a Mk262 Mod 0 clone (77gr Nosler CC) at nominal 18" 5.56 Mk262 velocity, a shot through the top of a deer's skull at 65yd and traveled 10" through brain, spine and neck muscle yet did show any obvious signs of fragmentation. The bullet clearly yawed and created an impressive wound, and the animal was very cleanly harvested with surprisingly impressive (to me) terminal effects. If 22 centerfires were legal in Indiana as they are in Kentucky, I'd absolutely not hesitate to use a Mk262 clone on deer given my personal experience.

However...

A 10.5" 5.56 shooting that same load is going to be moving 400fps slower, and obviously the decreased velocity will have a downside impact on fragmentation; will it also have a downside impact on bullet upset/yaw and therefore wound channel? My own research has been inconclusive, though again I acknowledge Mk18s loaded with Mk262 have proven plenty effective in combat over the last decade-plus. I suppose my concern would be with the long wound neck observed with Mk262 even at 18-20" velocity and how that would be amplified from a short barrel - something like a 5.56 pressure 77gr TMK (vs. SMK) would negate that potential concern over neck length.

It seems to me that, having the choice, using a bullet you KNOW will expand to double diameter at your weapon system's muzzle/impact velocity is a better option than a bullet you can't be sure will produce yaw and/or fragmentation terminal effects. Obviously YMMV, caveat emptor, etc....and God knows I wouldn't volunteer to be shot by any of the discussed bullets.

Good technical discussion!