The rifle is only one component in a two component system.  An SBR under 10-11" is poorly suited for 5.56 ammo, both in terms of terminal performance and blast/noise.  This can be partially mitigated by using ammo designed to overcome the terminal ballistics part, like 70gr+ TAP or other expensive specialty ammo.  A suppressor will reduce blast/noise.

I built a 11.5 AR pistol for use as an emergency carbine/PDW, but that's exactly what it is, an emergency arm to fight my way to my 16" rifle.

Here's my thread  Emergency Carbine

The P90 and its ammo are a MATCHED PAIR, and designed for a particular purpose: a PDW to defeat body armor at close or intermediate range.  The gun and ammo are designed from the ground up to complement each other.  Most 5.56 ammo is not designed to be effectively used out of a barrel less than 16 inches, both in terms of lethality and blast.  5.56 in any flavor is a rifle round, meant to be used in a rifle barrel.

don't be an ass and try to provoke with a straw man argument.





and Gene, you're welcome.  I'm now experimenting with red dots on top of the carry handle.  it will really aid in sight aquisition.  But I can whack a 6" gong at 100 yards all day long if I take my time and use the small aperture.

Quoted: Quoted: The rifle is only one component in a two component system.  An SBR under 10-11" is poorly suited for 5.56 ammo, both in terms of terminal performance and blast/noise.  This can be partially mitigated by using ammo designed to overcome the terminal ballistics part, like 70gr+ TAP or other expensive specialty ammo.  A suppressor will reduce blast/noise. I built a 11.5 AR pistol for use as an emergency carbine/PDW, but that's exactly what it is, an emergency arm to fight my way to my 16" rifle. Here's my thread  Emergency Carbine The P90 and its ammo are a MATCHED PAIR, and designed for a particular purpose: a PDW to defeat body armor at close or intermediate range.  The gun and ammo are designed from the ground up to complement each other.  Most 5.56 ammo is not designed to be effectively used out of a barrel less than 16 inches, both in terms of lethality and blast.  5.56 in any flavor is a rifle round, meant to be used in a rifle barrel. So if you were shot in the chest twice with a 75gr TAP from a 11.5" barrel vs a 16" at 50 feet what would happen? I'm just curious. Bounce off? Flesh wound? You laugh? I'd like to know. Does being shot in the face by 5.56 from a 7" PDW barrel just mean you dont need to shave one cheek the next morning? Since it isnt effective you can shake that stuff off right?

You're still acting like an ass, but I'll explain since you persist, and only to those besides you that may be interested.

You drastically oversimplify the argument in order to win.  Nowhere did I say any ammo/rifle combination was devoid of effectiveness.  It's called a straw-man argument.  You falsely characterize my point in such a way as to be extremely vulnerable and then attack it with much (superfical) success and ease.  Like setting up a man made of straw and attacking him instead of your real opponent, who is not so weak and can fight back.

the 5.56/223 cartridge is designed to be a rifle round, as opposed to a pistol round or something else.  It's shape, weight, charge, etc are designed based on use in a rifle.  If fires a slow burning rifle powder.  It fires a rifle type spitzer bullet.  It employs a rifle-type bottleneck case.  All of these factors generate some liabilities when you try to make it function correctly out of a pistol length barrel.  Here are a few I come up with

1. lots of unburned powder left over after the bullet leaves the barrel.  This powder that would normally combust inside a longer barrel now combusts more violently in the air in front of the muzzle.  This creates a very real flash/blast problem for the shooter, especially indoors.  Fire a rifle caliber indoors and you risk loosing you hearing permanently

2. dramatically decreased bullet performance.  This is more pronounced in calibers that rely on velocity to produce fragmentation and such.  Since the barrel is short, the powder is not able to completely burn inside the barrel, and lots of what would be useable energy to drive a bullet faster in a longer barrel is wasted making the air in front of a short barrel hot and sparkly (see #1).  So bullets that rely on minimum velocity to perform have their effective range severely reduced or dropped to nothing.  I'M NOT SAYING THAT IT WON'T WOUND AT THAT RANGE (nitwit) BUT THAT IT DOESN'T PERFORM THE WAY IT WAS DESIGNED.

It's a give and take.  You want a shorter barrel, you have to give up a little bit of something else.  How much is too much?


Now, several things can be done to LESSEN the impact of those factors.

1. you can add a sound suppressor.  You can add a flash hider.  You can wear ear protection and sunglasses.  You can use low flash & fast burning powder in your ammo (but not so fast you would blow up a rifle if you fire it in a, a... a rifle!)

2. you can limit your range to the effective distance of youf rifle/ammo combination.  You can use different projectiles that are LESS dependent upon velocity to perform.  you can switch to 5.45 (JUST KIDDING!)


But these are all accomodations for existing liabilities, and none of them fully FIX the problem or ELLIMINATE  the liability.  It is an adaptation of an existing system to do something that it was not truly designed for.  


This is all rooted in the concept of the P90 being built from the ground up as a PDW.  Both the weapon and the ammo were designed to function out of a short barrel at intermediate distances to defeat body armor.  As such, it does that very well, but it does not perform well as an assault rifle, becuase it wasn't designed to be an assault rifle, just like an AR wasn't designed to be a PDW.  You can make it one, but not without inherent limitations.

You can make a Chevy truck run on railroad tracks by some creative engineering, but it wasn't designed to really do that, and doesn't do it as well as a locomotive.  But you wouldn't expect it to.

PS.

Don't forget that I own a 11.5 AR specifically for use as a PDW.

But I know it's limitations

They are VERY specialized item (in fact I cant really see the point beyond 1 or 2 roles none that are relevant to a civilian)

BUT they are damn fun to play with...

I've shot 4" to 20" M16 setups and Hk53, Hk G36C, Sig552 and a 11" FN FAL (not sure why)

As a tactical weapon they demand a suppressor - which in turn lengthens the weapon by 4-8" depending upon the can you have.

M2 Corp had 4" and 6" PDW's but I dont think they are operating anymore --




and a homebuilt by the CF's LCMM SA

note the forerunner to the Diemaco PDW butt...


Wes Grant (MSTN) had some 7.5" uppers that he was selling - IMHO that woudl be a much more reliable option that the DPMS Kitty Kat -- I've played with 10 different ones of those and NONE ran well without some tweaking (like redrilling the gas port...)

Where to get a krink brake?  I'm seriously thinking about replacing the phantom on mine, which, BTW, almost elliminates flash from even the 11.5 barrel!

but blast is another matter

my PDW for the variablebinary





read the emergency carbine project thread for philosophy and build details

thanks!  How would you rate its effectiveness?

nevermind.  i found the noveske thread

Quoted: If you can afford the tax stamp, why not just go short barrelled UZI? Or a Greasegun in .45 ACP? More punch at close range, I'd bet, than a greatly slowed down 5.56 at close range. And more compact.

Uhm no.

Mk262 out of a 7.5 will still frag out to about 15m IIRC.


The PDW conceprt was to allow CSS pers to have a compact weapon that still gave armor (soft) penetration.

I still think 10" is the shortest really useful 5.56mm gun - but I'd never handicap myselft with a 9mm or .45 subgun