For some reason, my 3rd gen S&W's do not function well with snap caps. I had a 3913 once that would lodge the snap cap into the barrel after repeated strikes, and my 5903 is currently sent in for an inspection because using snap caps in that makes the firing pin stick. The pin will not pop out again after pulling the trigger. These are AZoom snapcaps and they have only been used a few hundred times. They're supposed to be good for over 1000 trigger pulls.