A capped case , a pound coin , a block of hardwood , a penny is all you need to test the efficiency of any double gun striker. When you have eliminated all other possible reasons for a misfire . Broken worn mainsprings , damaged return springs ,worn or broken strikers /fire pins , gun not cocking fully or something preventing the hammer from falling correctly , dirt etc. Hard primers are the most common fault . Basically what you have in your pocket or on your bench .