I have the aim point catridge laser,comes with the 223 laser then you buy the catridge size needed, it fits over the 223 laser and slide it into your chamber. Works best at dusk and dawn. Directions says to close the bolt but I dont because I'm afraid it will get really stuck,I just slide it into the chamber firm but I still need a cleaning rod to push it out. I tune in from 25-100yds and it will put me at an inch or less on target.
the problem I have with these particular bore sighters is that the batteries seem to run out pretty fast. practically every review i've read for this type of laser sighter was negative.