Also not trying to be a jerk, but RTFM... Page 17
DRY FIRING
Going through the actions of cocking, aiming and pulling the trigger on an
unloaded gun is known as “dry firing.” It can be useful to learn the “feel” of your
pistol. Be certain that the pistol is fully unloaded (both the chamber and magazine
are empty) and that the pistol is pointing in a safe direction even when you are
practicing dry firing. The RUGER® P345TM pistols can be dry-fired without
damage to the firing pin or other components as long as the magazine is inserted.
You can dry fire it without a snap cap. Snap caps are for guns that CANNOT be dry fired, such as my Kel-tec PF9. You can use a snap cap if you want in your p345, but it will be redundant...