I've had my M2 for quite a while & felt comfortable with it on my pistol. One day while getting ready for the range, I decided to shoot my .45 with the M2 mounted on it. I wanted to see if it changed my POI and if the center of the light happened to line up close to the POI. After a few shots, it had come loose from the pistol rail. I was not happy, imagining me trying to defend my house and after a shot or 2 the light may flip right off the gun. I must add that I am not sure it was fully seated, since it didn't do it the second time I took it to the range. The second trip with the light (I wanted to try it again), I went through 150-200 rounds. When I went to clean the pistol, I tried the light...no light. Upon closer examination, the bulb had unseated itself. I removed the light head & reseated the bulb. It works now. The thing that gets me, is that this is designed to be used on a HK pistol rail. I used an HK & had an issue both times. I'm not feeling the love for this light. I have not contacted Insight yet, so I can't say that they won't do anything to fix or replace it. But, I'm not optimistic, as I no longer have my receipt. Moral of the story: If you have a light you plan to use on your gun, you should probably give it some range time to see just how durable a product you have.