So the story is Wetzel could load and fire while fleeing from Indians. He allegedly did so killing or wounding several Indians chasing him . This was an emergency procedure.
Wetzel was reported to place several round balls in his mouth, and to spit the ball into the barrel, after adding powder, slam the butt of the rifle upon the ground, and then turn and shoot one of the pursuing Indians.
Folks have experimented and it has been found to work BUT..., there are some special conditions. First, the frizzen is shut on an empty pan. Next the powder is poured into the muzzle from the horn. This is dangerous especially because after the first shot followed with a rapid reload the shooter is risking a premature discharge. Next, the ball is spit from the mouth but NOT directly into the barrel.
Holding the mouth up to the barrel and trying to spit a ball into the muzzle was found to be a good way to knock out a tooth or two while running over uneven terrain. Usually the ball failed to go into the muzzle during testing. The solution was found; the shooters "off" hand is held at the muzzle and the ball is spit into the hand, and the hand then guides the ball as it drops into the muzzle. Then the rifle butt is tapped several times against the ground while continuing to run (hopefully not breaking the stock at the wrist or causing other stock damage) which then hopefully seats the unpatched ball on the powder at the breech. The pan on the lock self-primes at the same time because..., the touch hole is overlarge from use. The rifleman need only to cock the piece, turn, and to fire. Not a very far shot, but one can hit a man sized target in the chest at 25 yards and perhaps farther with an unpatched ball in a rifle.
Wetzel didn't carry ball all the time in his mouth, so he wasn't sucking on lead all day.
Another account is that some men would hold ball between fingers jammed where the fingers meet the hand, and over time the hand changed and it was possible to hold the balls in that hand without much discomfort.
LD