Bisley alloy snap caps are used to take the pressure off of main springs in shotguns. Used in the same way as a cartridge, you pop the snap caps into your gun once you have finished cleaning and release both triggers. The firing pins strike a small brass dummy primer which is connected to an adjustable spring taking all of the pressure out of the main springs.
Perfect edition to any cleaning kit.
Prolongs the life of your gun’s main springs.
A good idea when storing a gun for any length of time.