What batteries are you using? I have heard of similar problems stemming from the use of non-surefire replacement batteries i.e. two seperate batteries. Something about them coming apart just enough from the recoil to cause an arc across the two battery contacts with in turn causes a short "surge" across the bulb, causing it to fry itself. How old is the light? They all burn out at some point, but if it's fairly new, and you're using the supplied battery (looks like a 1 piece unit, but actually two piece bound by heat shrink tubing), and you can verify that the bulb is truly dead, give surefire a call and tell them about it. They may send you a free replacement. I've got three of their forearm housing/6v light pkgs, and I have yet to burn one out after a few years and several hundered rounds.