If you are sighted in at 25yds, and you shoot a target closer, the amount of vertical difference from poa and poi could only be less or equal to the amount of space between the muzzle and laser lens, 2 inches at best I would think. At 50yds (I think) you would only be shooting high by that same distance. I figure that at less than 25, the BG isn't going to care if you hit him in the nose, forehead or throat. Sure if you have some type of hostage situation it could be a problem, but thats why you keep your sights on the gun when you install the M6. Not meaning to flame anyone, just my two cents worth.There is one serious drawback which I am surprised more people dont mention--- It can only be zeroed in at one specific distance! Due to the distance it sits under the muzzle, the laser points upwards to some degree. As I recall, Streamlight recommends zeroing it at 25yards. Thats all fine and dandy, but at distances less than this, it will shoot low (several inches). This is very pronounced if you aim at say, 10 yards. Likewise, if you were aiming at 40yards, it would aim high.