After using this thing a bit, and comparing it to my caplocks, I have to wonder why anyone stopped using flints. The mechanism is absurdly simple. English flints are best, but many other types of flints and rocks will serve well enough.
I guess wet weather created problems, but with a flint you just have a knee over the lock or put a fresh charge in the pan before firing. If wetness gets to a caplock you're out of action for a while, esp. with a complex patent breech. With the flinter there's just a simple hole to be cleaned out from time to time, and a pan to brush.
"Know that the pistol has no value, we practically don't use it. We need grenades, rifles, machine guns, and explosives."
Mordechai Anielewicz, April 23, 1943