I'd never read this before:
(M21) Does the registered owner of a destructive device, machine gun, short-barreled shotgun, or short-barreled rifle need authorization to lawfully transport such items interstate? [Back]
Yes, unless the owner is a qualified dealer, manufacturer or importer, or a licensed collector transporting only curios or relics. Prior approval must be obtained, even if the move is temporary. Approval is requested by either submitting a letter containing all necessary information, or by submitting ATF Form 5320.20 to the Bureau of ATF, NFA Branch. Possession of the firearms also must comply with all State and local laws.
[18 U.S.C. 922(a) (4), 27 CFR 478.28]
So you can get them but can't take them anywhere. Great. Glad I've been able to resist the urge to buy.
Also this is awesome:
(M30) Are Paintball and/or Airgun Sound Suppressers NFA firearms? [Back]
The terms "firearm silencer" and "firearm muffler" mean any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication.
Numerous paintball and airgun silencers tested by ATF's Firearms Technology Branch have been determined to be, by nature of their design and function, firearm silencers. Because silencers are NFA weapons, an individual wishing to manufacture or transfer such a silencer must receive prior approval from ATF and pay the required tax. See Questions M15 and 16 for application details
That should put an end to all those hits being done with paintballs