(Assuming of course that the pistol still looks like a pistol, ie: exposed slide&muzzle)
I did not know that, glad this came up.
Any Other Weapons (AOWs)—this is a broad “catch-all” category used to regulate any number of firearms which the BATFE under the NFA enforces registration and taxation. Examples include, among others:
1) Smooth-bore pistols 2) Pen guns and cane guns 3) A firearm with combinations smooth bore and rifle barrels 12 inches or more but less than 18 inches in length from which only a single shot can be made from either barrel. 4) Disguised firearms 5) Firearms that can be fired from within a wallet holster or a briefcase 6) A short-barreled shotgun which came from the factory with a pistol grip is categorized as an AOW rather than a Short Barrel Shotgun (SBS), because the Gun Control Act describes a shotgun as “…designed or redesigned to be fired from the shoulder…” 7) Handguns with a forward vertical grip.