Would you trust your life with a 9" Pistol Upper in a gunfight

[Dumas1012]

After shooting my braced m92 this weekend. I would take that it over my AR pistol if shtf. I was ringing 8" steel very loud at 100 with open sights.

[junior40er]

using an AR pistol in a real fight would be a NIGHTMARE

[SNCaliber]

why not, a 9" SBR AR would work great in sub 150 yd i think

[Sniper3142]

Lots of folks in uniform use MK18s with 10.3 inch barrels to great effect. Ammo selection is VERY important.

From 300 yards and under, I'd rather not be on the receiving end.

[G21Shooter]

Dude .22 lr is deadly at 150 yards, .223 from a 9 inch barrel will be as well.

That said in the unfortunate event one has to use their AR for anything other than hunting or paper killing at the range, a over 12 inches is the ideal length(for reliability sake).

[deckhandmike]

I trust my pap92 more than any semi auto I own. It's my go to when shtf.

[Germz]

Where do you people come up with these questions.

[MrPlink]

What gun does the other guy have in this fantasy.. err I mean "scenario"

[akjunkie]

Mods need to make the AMMO ORACLE a sticky. The Ammo Oracle should be required reading for anyone that owns a AR.

Fragmentation:
"Unlike most FMJ rounds, M193 and M855's primary wounding mechanism is fragmentation"

http://www.ar15.com/ammo/project/term_m193orm855.html

Minimum Velocity for Maximum Fragmentation:
"Between 2,500 fps and 2,700 fps, the bullet may or may not fragment and below 2,500 fps, no significant fragmentation is likely to occur"

http://www.ar15.com/ammo/project/term_velocity.html

Velocity/ballistics from Military ammo.

http://www.ar15.com/ammo/project/perf_ballmil.html

What range M193/M855 will fragment.

http://www.ar15.com/ammo/project/term_fragrange.html

Not all 5.56 created equal. Some wont Fragment at all.

http://www.ar15.com/ammo/project/term_2700.html

Twist rate.
"At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight."

http://www.ar15.com/ammo/project/perf_whattwist.html

Anyone remember Blackhawk down? Army Ranger shoots 3 Skinnies on 3rd burst. Each Somali takes 3 hits (@ 50yds). 2 got back up and carry the 3rd back to safety. Bad combination of rifle length, twist rate, velocity, ammo type, etc.

[gunception]

I went with a Spike's 11.5" barrel upper for my go-to gun, but it's finicky with ammo so I wouldn't trust my life on it. Still the PAP M92 for me as well if I had to choose a shorter barreled semi.

[sunborder]

I don't think you can easily get those kinds of velocities out of a 9" barrel, even with hand loads. 10.5" barrels seem to be about the sweet spot, where you start getting rifle-like velocities out of AR pistols with the 5.56. And inch and a half doesn't sound like much, but it seems to make a huge difference it terms of performance. I doubt you would be able to break the 2,000 fps mark at the muzzle with a 9" barrel. Whereas you could reasonably expect 2,100-2,200 fps with the 10.5" barrel using standard rounds.

There was a thread a ways back where a guy cut his barrel down 1 inch at a time. He was getting 2800 fps from a 10" barrel with handloads (H335 I think).

M855 out of a 10.5" gives about 2600 fps (see http://www.sadefensejournal.com/wp/?p=1093). M193 tends to be about 100 fps faster than that. That's 2700 fps with military ammo designed for 20-inch barrels. With judicious testing of various powders, I don't see why someone couldn't push that velocity a bit without the loads getting too hot. It's about matching your burn rate to barrel length without getting pressure too high. That's still a far cry from 2,000 fps. Then you can have fun using superior civilian projectiles (varmint/hollowpoint) rounds that will reliably fragment at velocities that M193/M855 won't. The only reason to *adamantly* stay at 10.5" + is if you plan on using factory milspec ammo.

So why do DEVGRU operators use a 10.5 barrel on their HK416's? Because it's not lethal enough? Better go ask Osama Bin Laden about how effective a short barrel can be.

They use those weapons when they plan to be clearing rooms or the inside of commercial passenger airplanes, where maneuvering is more important than reliable fragmentation at 150 yards. 2,600 fps starting velocity means no fragmentation by the time you get to 50 yards. OBL was shot at less than 10 yards, by all accounts. Those "Operators" you are talking about bring a longer barreled weapon if they plan to shoot at 150 yards, at least, if they have any say in it.

[0321jarhead]

What gun does the other guy have in this fantasy.. err I mean "scenario"

Where do you people come up with these questions.

I could'nt agree more with this subject! Perhaps the OP should just enlist in our military to get a reality check. That way one could really learn something.

[NapalmCheese]

I, personally, love the method by which most people on here seem to determine the terminal ballistics of any rifle/ammo combo they choose to use. Forget about math and physics, I 'hit gongs all day long at 300 yards' and 'ring steel super loud all day long'.

Let's just apply a little math to this problem.

Mk262 fails to fragment under about 2100 fps, and M193 fails to fragment under about 2600 fps.

If we believe what This site has to say, you can expect 2600 fps from a 55 grain projectile out of a 10 inch barrel at .223 pressures. There's no data for a 77 grain load, but assuming you can move it at 2700 fps out of a 20 inch barrel, let's assume you lose 25 fps/inch, we're losing 250 fps moving to the 10 inch barrel. That's a muzzle velocity of 2450.

Plugging those numbers into jbm, you cross under 2100 fps at about 175 yards with about 770 ft/lbs of energy.

Would I want to stand in front of either of them? No. If I had to choose one to be shot with, I'd choose the short barrel with M193 as it would be the one most likely to pencil through.

How about at 150 yards? I'd still rather be in front of the 55 grain bullet, as it would likely pencil through AND have less energy (not that it matters much if there is no expansion or fragmentation), as such without a CNS hit my chances of making it to a hospital and recovering are greatly enhanced.

Would I hunt deer with either of those? Not on purpose. I've never hunted with fragmenting ammo and the penetration numbers I see from Mk262 don't make me think it would be useful for anything other than broadside lung shots under 150 yards.

[JDW67]

Well, to be honest, if it were a SHTF situation, I have "other" rifles that I would grab.

[RobertMW]

So why do DEVGRU operators use a 10.5 barrel on their HK416's? Because it's not lethal enough? Better go ask Osama Bin Laden about how effective a short barrel can be.

They also have ready access to rounds like the Mk. 262, which is firing a 77gr. OTM bullet that fragments reliably at much lower velocities, and the Mk. 318, which is of similar construction as the Federal Trophy Bonded Tip line.

Both will fragment/expand more reliably than m193 and m855/A1 at low velocity, although the reports are saying that the M855A1 is performing well terminally, at least better than M855, even though it is beating the crap out of guns.