I recently added the Crimson Trace LG-405's to my 642. I took it to the range the other day to get it aligned properly. Everything went well until I started doing rapid fire strings. About half way through the 5 shots the laser would quit. I would check the master on/off switch and it would be in the cut off position. The first time it happen I thought it was just a freak occurance. Well it ended up happening about 3 more times. Each time the switch would be fully in the off position or partially but enough to cut it off. The switch seems to have a decent amount of friction to being moved and "clicks" when moving from on/off/on. It seems unlikely that the recoil was enough to be moving the switch so I guess I'm gripping it tight enough that my hand is being squeezed up into the recessed switch cavity and moving the switch.
I called Crimson Trace to discuss the problem. They said they had never heard of that before. They are sending out a replacement and I'm to send this one back. I guess if this one does it as well, it's me. If so, the only thing I know to do is cut a small piece of rubber and wedge it behind the switch to keep it from moving to the off position.
Has anyone ever had, or heard of this problem?