LOCKING UP THE GUN.

Years ago I had a percussion cap drive a Lee REAL bullet into the barrel of a Ruger Old Army. There was a problem with contamination of the not factory approved powder load by the lube used on the cast bullet. My guess is that there was enough powder ignited that it contributed to help drive the bullet past the forcing cone. This was followed by a full charge of non factory approved powder that did not suffer contamination from the lube and drove into the rear of the first bullet at non factory approved pressure and velocity levels causing both to "exit stage left" - right out the side of the barrel. Sometimes I wonder what the guys at the repair center thought/said when they unwrapped it prior to replacing the barrel. It was as good as new when they were done, but got sent down the river in exchange for more modern armament.

Anyway, a primer only would probably only drive it far enough forward to block the cylinder. If there was a tiny amount of powder ignited it could drive it further into the barrel and cause a bore obstruction situation. There's a good reason why one should examine carefully a sixgun (or any gun) after not observing the effects of a bullet leaving the barrel upon firing or observing an out of the ordinary recoil (or lack thereof) upon firing.