Depending on the length of the hand guard. The total length is 7” and you need at least 9 slot rail. So an AR pistol with a 7.5” barrel and lower won’t cut the mustard. As far as the legality goes, this is not a vertical fore-grip so feel free to slap this puppy on your AR pistol with a total length of less 26” from the end of the buffer tube to the end of the barrel or end of the manufactured muzzle device that cannot detach. ATF can SMD