The reason the 45/410 barrel are legal is the fact they are rifled and not smooth bore so they are still a legal .45 caliber handgun with a chamber long enough to take a .410 shell. For a smooth bore to be legal it has to have at least 18" of barrel and 26"or 28" or overall length. I don't remember the over all length for sure. A shotgun under the 18" barrel length or over all legal length is classed as an AOW (Any other weapon) and requires the same forms and tax papers as a machinegun. Maybe someone else can give you the exact over all length. Some of the laws on firearms and related things don't seem to follow logic at times but they are still the law. A good example being the same thing applies to rifles with barrels under 16" of length. Where is the logic in a short barrel rifle being against the law when a handgun is smaller and something that can be carried in a persons pocket? It is illegal to put a stock on a handgun, that would make it too big to hide in your pocket and harder to hide. We have a lot of laws on the books in this country, not just gun laws, that are really funny if you read them. Makes you wonder just what the people that wrote them were thinking, but laws are just that and to stay out of trouble you must obey them. You can find the Federal laws by doing a search on the government listings. Better to be safe than sorry.
