Well if you're out hunting, or on a woodswalk shoot, not walking about with an unloaded gun, then you have the main charge and the projectile(s) in the breech. No way to go from one end and out the other. Now a revolver, sure, just pull the cylinder after removing the caps and clean the barrel on the frame, but a caplock or a flintlock rifle or pistol...., you'll need to unprime or uncap, and then break up the dirt in the muzzle and allow it to drop free. IF you are going to unloade the gun or rifle, then one of those CO2 dischargers would blow out the main load and dirt in one step...and you can reload from scratch.
LD