Well, It requires hard to find ammo, but the Pietta PPS-50 "Puma" can use a 50 round drum mag. Needs "High Velocity" ammo. Found it feeds best with rounds that have a muzzle velocity over 1400FPS.
Just click on Marstar's link up top. Though their site's not working for em atm.
This is how I got it. Red dot(Though I think I'd prefer a real optic), bipod(It's handy, it's NOT a light firearm), foregrip, and polymer collapsible stock.
I keep it in a full on gun case, as it's an "evil" looking firearm, and don't want any nosey nancies calling the cops.
but EVERY friend/family member who's tried it, loves it. But be warned, you spend a LOT of time loading ammo.. 50 rounds go REAL quick.. You might wanna get 2 or 3 extra drum mags, so friends can load while someone's shooting
And it IS non-restricted, though I doubt most LEO's would believe it unless they were into firearms enough to KNOW the laws.