Not at all; they're sold mainly for exterminating rats, mice, and snakes, but if you try a few at even 5 or 6 feet against a paper target, you'll see that they're pretty useless even for that. A smooth-bored handgun that fires a SHOTGUN SHELL, OTOH, can be fairly effective, and were pretty popular before the NFA made them "controlled items" in the 1930s. You can get to one of those in 2 main ways; either as a SBS/"short-barrelled shotgun", or as an AOW/"any other weapon", which differ mainly in whether they were made from an existing shotgun or built from a bare receiver. These aren't "illegal", but they do need to be registered and have a tax paid on them when you buy them.