The green laser boresight in223/556 and blackout is compatible with 223/556 and blackout calibers. Once chambered, it will project a green laser to show where the point of impact is. Adjust your AR optic, red dot, riflescope or tactical laser until it lines up with the crosshairs of the optic you are sighting in. DO this at 25 yards and at 100 you will be within inches of the target, depending on barrel length, grain and type of ammunition. More information on the Laser Boresight article.