And remaining completely non-political on that topic there is actually a reason as to why in the US short barreled rifles and shotguns have more restrictions than a pistol. The reason being that when the law was originally drafted it was to have included pistols as well, but due to opposition that was dropped from the law.
To the OP you would need to contact I believe the ATF (someone correct me if I have the organization wrong, I don't deal in American gun laws) to find out what has exemptions to the short barreled rifle categories. Things like some C96 Broomhandles, and Inglis Hi-Powers have exemptions but you would need to verify what is and isn't exempt.