Hey guys got a line on anAR lower marked pistol might pick it up incase they are not around in the future. What are some good calibers for an AR pistol was thinking good old 5.56 lets here your chocies.
That's sounds like a good plan. Spike's sells a "Concussion" pistol model that's pretty cool looking. They sell the upper also. You can also get complete uppers from LMT and RRA among others so you have some choices. A really short barrel may not get you the velocity you want to expand 5.56 bullets. I guess it depends on what you want it for.
9mm is another option, and 6.8 can be done also. How about going big with a 458 SOCOM pistol? :lol:
A contractor that we use to talk to in Iraq had a AR based PDW chambered for .45 acp it had a 9.5in barrel no but stock and a forward grip on a shorted rail it was on a ZM upper with no buffer tube it looked cool he sed he liked it . he never let us fire it tho. do not know how reliable of a bolt it could have tho to fit a .45acp in a ar bolt you would have very little room left on the bolt. on mags he sed it used .45 cal UZI mags
In a short barrel,
a bigger ( diameter ) bullet it better
because it allows more velocity for any given bullet weight.
As Art said, in you will have pretty low velocity in a 223, as well as a lot of flash/blast in a 10.5" bbl.
It is probably one of the poorest choices in a short barrel.
IF you want to stay in the relatively powerful intermediate rifle cartridges and keep/reuse your mags,
a 6.8 or 7.62x39 would probably both be better choices, depending no your intended purposes.
The only other issue with such short barrels is that the DI system is at/beyond its limits and a piston system is better.
If you want to have a much less potent ( and less expensive ) cartridge,
a 9mm, 40 or 45 are good choices and a 10.5" bbl is considered long for a pistol, so velocity will be high and blast low.
These all use pure recoil operation so there is no short gas system to worry about
but you will need a magazine adapter and new mags.
Come to think of it, the AR57 upper seemed like a pretty slick solution with top mounted 50 rd magazine and integrated recoil spring. Perhaps someone should make that in 40s&w, because I can't come up with a good use for the FN 5.7x28
Your best route depends on what you want out of it.
There used to be an outfit called "CNC Gunsmithing" that made an 80% billet lower that they called the AR-45. It used M3 grease gun mags and works well. The same mags will work with the 10mm as it's only .030" longer if you modify the feedlips slightly to insure that the round will stay in place. I did have to sort through the mags that I had just to make sure that that extra .030" didn't bind partway down.