I believe TC solved the pistol/rifle thing long ago, all of their receivers are legal to have pistol length barrels installed with pistol grips, the thing you have to avoid is putting a rifle stock on with the pistol length barrel, thats a "short barrel rifle" or "SBR" and is a class 2 weapon. I dont know of any state statues that restrict how the rifle was configured at the point of first sale since all TC Contenders/Encores are registered as pistol frames. Kinda grey I know, but I think the ATF has other things to chase down. Now if they were all black and had bayonettes.....
Anyway, its a great system to play with, I just wish the barrels were cheaper! Good luck-pbgunrunner