not on most as there would be no way to mount it you would need a top mounted rail or other modified mounting system

Taron. no, this can be mounted on a Weaver or Picatinny mount which mostly long guns have and not handguns. There are adapters but are expensive to get mounted on a pistol.

Taron - yes, it could be mounted on a .45, however I would personally not put this red dot on any firearm other than a rim fire 22LR or 17 HMR. I'm just not sure how much shock it could take, and still function properly. This red dot got some pretty harsh reviews .. and I believe it has been discontinued by the manufacturer.