I have a 1974 production Rem 700 that I conservatively estimate has had 100,000 dry fires with no snap caps. It still works fine. Some shotguns, particularly doubles and most older 22's don't handle dry firing but it won't hurt most modern firearms at all. But always read the instructions. Kel-Tec does not recommend it on at least some pistols, and the Ruger 345's could be damaged if dry fired without a magazine in the gun. With an empty magazine it won't hurt it at all. This was due to an unusual type of magazine safety on that model Ruger.