dry firing in centerfires of modern manufacture user preference. ive never seen or heard of damage in a modern centerfire from dry fire. in a rimfire it can ding up the chamber edges or the firing pin itself to such a state as they are unusable or even make slam fires a possibility from sharp edges on the chamber walls. my .22's all have dings in the chamber edges from forgettting that it is a .22rimfire and just snapping the trigger after a safety check. so far no real damage that i care about but i keep a close eye on sharp burs developing. its a bad habit i cant seem to break.