What does for rifle and shotgun lights and kills them dead is the repeated recoil. For true dependability in a crisis life or death situation, only a dedicated shotgun light will do, ideally permanently mounted on (ie, in) the fore end. Can't go wrong with the Surefire version, if you can find one. I have a older Streamlight very similar to the forend replacement one I see is currently available and it works just fine. I also suggest that a light operating with lithium batteries, ie the CR123s both the lights mentioned use, is the best option due to their 10 year shelf life, power, and the fact that they won't leak even if unused for years.