A snap cap
is a device which appears similar to a standard firearm cartridge
but contains no primer
or projectile and is used to ensure that dry firing
firearms of certain designs does not cause damage. Snap caps contain a spring-damped false primer which absorbs the force from the firing pin, allowing the user to safely test the function of the firearm without damaging the components of the firearm.
A small number of rimfire and centerfire weapons of older design should not be test-fired with the chamber empty, as this can lead to weakening and possible breakage of the firing pin and increased wear to other components in those firearms. In the instance of a rimfire weapon of primitive design, "dry firing" can also cause deformation of the chamber edge. For this reason some shooters use a snap cap in an attempt to cushion the weapon's firing pin as it moves forward.
A pair of 12 gauge snap caps
Snap caps and action-proving dummy cartridges also have usage as a training tool to replace live rounds for loading and unloading drills, as well as training for mis-fires or "jams", as they function identically to a live "dud" round that has not ignited
Maybe I missed it in your information......if so, please forgive, but........can you re-use these over and over, or are they a "use once and throw away" kinda thing? (My guess, if I had to "guess" would be that the manufacturer would render these useless after one shot, in order to get folks to buy more.........lol).
"If the river sounds; somethings coming"