Two handed grip = any other weapon?
Say Uncle posts on a court ruling that a pistol with a vertical forend grip is not "any other weapon" under the NFA.
"Any other weapon" requires application and registration, as with a machine gun, altho the transfer tax is only $5 as I recall. It's a legal quirk that originates in the history of the NFA. NFA as introduced in Congress would not only have covered MGs and short barrels, but also handguns (at the $5 rate). To prevent quibbling over what was a handgun, it added and any other gun capable of concealment on the person. Congress stripped the handgun part out, but forgot to take out and any other weapon. So all the obscure palm guns and cane guns and anything that isn't really rifle, shotgun or pistol, has to be registered. ATF's position. ATF takes by regulation the position that a pistol is a gun intended to be fired from one hand, and so putting a vertical forend on a pistol makes it a two handed gun, and AOW rather than a pistol. From his report, a court has ruled this isn't so.
Congress sometimes does nobody (gun owner, ATF, or anyone else) any favors when it writes law. Esp. laws that wind up governing very obscure firearms. A .44 mag is just a gun. A .32 rimfire palm gun that uses ammo not made in near a century, and which its owner wouldn't dare fire for fear of breaking a part and reducing its value, winds up with federal registration, send in your fingerprints for a full FBI check, etc.
Hat tip to Sebastian...