I have a Wheeler green laser magnetic bore sighter. It also comes with a highly reflective 12"x12" graph to be easily seen in daytime. Use it for every new sight i mount. It goes on the end of your muzzle not inside bore. Works great unless you forget and buy a SS muzzle break LOL.
Its only to get me on paper, thats all most bore sight companies say anyway. I still fine tune my optic the old fashion way once on paper. You can waste a lot of ammo sighting in a new optic......