I have picatinny/weaver type rails on all my guns (centerfire/muzzle loader/shotgun) and my single FastFire gets used on all of them. So long as the gun’s dedicated scope is zeroed in, then it’s a snap to remove it and install the FF in its place. (Immobilize the gun and pick a target through the scop, remove the scope, install the FF and zero in on the target without moving the gun. Bingo!) Did this and got a deer with my shotgun. Love that FF!