.30 USC handgun
Daren--
Some years back, in the 60s or 70s, I believe, they marketed such a pistol, called, I think, The Enforcer. Not a bad-looking piece, actually As the manufacturer set aside certain serial numbers to be used for PISTOLS, this is (was?) entirely legal--they never had long barrels nor shoulder stocks. This is pretty much the same thing as the Remington XP-100: What would normally be a rifle action (Remington 600,) but intended before manufacture to be a handgun.
You don't sound like you're considering any such project, but a couple of cautions for other readers:
***Do not set out to make one of these on your own. A shortened CARBINE barrel, in company with the action, becomes a short barreled rifle and subject to National Firearms Act regulation. (Barrel under 16 inches, or under 26 inches overal length without regard to barrel length.)
***Also, if you DO come up with an Enforcer, resist the temptation to put it into a shoulder stock for increased accuracy, or whatever. This also makes it a SBR, etc.
Best regards,
Johnny
MOLON LABE