The main reason I don't like weapon mounted sights is the simple fact that they would make for a excellent aiming point(source of light)for the bad guy to shoot at. Rest assured if you are trying to clear a room and the bad guy is already in there,he has the advantage of knowing exactly where you are at-especially with a weapons mounted light. I prefer to hold light in weak hand,offset from body-that way they'll likely shoot at source of light and miss you.