Originally Posted by daswig

So much misinformation, so little time. A DD is anything with a bore over half inch diameter that doesn't have a "sporting purpose". "Sporting purpose" generally means things like shotguns. There's no such thing as a "destructive device permit". If you buy a destructive device as a private individual, you do it on a BATFE Form 5320.4, with the $200 tax paid, or if you have the appropriate SOT status, on a Form 5320.3, tax exempt.

With your 37 mm example, those are generally not seen as destructive devices because of the nature of the ammunition available for them. If you were to handload an anti-personnel round for a 37mm launcher and possess it in conjunction with an appropriate launcher, you would indeed most likely find your ass in the Pokey for possession of an unregistered DD if you didn't file a 5320.1 first and have it on hand and approved prior to constructing it. As long as it's a signaling device, it's not a DD. If you turn it into a weapon, a 37mm launcher IS a DD. Same deal with "bang sticks". If you're in the water and use it on a shark, it's not an AOW. If you take the head of it off and carry it around as a self-sefense weapon against humans, it's an AOW.