[ArtFWTx]

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:

 

[ArtFWTx]

I think Olympic Arms makes a 45acp upper. The lower and magazine well block, I'm not sure on where to go for that. Hahn Precision may make a 45 mag well block.

RRA does have a 40SW upper coming any time now using mags they designed. Can a 357 Sig version be far behind?