I have a simple little Sightmark 9mm laser bullet. I load it in the bore, close the action and then line things up across the basement. I don't have a red dot on it, I have lasers on my wife's pistol. So I just adjust the 2 red dots to line up on the far wall. I do rotate the bullet laser 0, 90, 180, 270 degrees everytime in case it has lost its centering, but so far it's good. Works great and it's cheap, especially when sales are running.