I don't get your point or question. In all conventional firearms (weapons that use a cartridge with a primer, powder, case and bullet) the "hammer" (firing mechanism) strikes a primer which makes a "small explosion" which ignites the powder, causing it to become a gas, the pressure of which "pushes" the bullet down the barrel and on its way to the target. The only way a pinfire cartridge differs is that the firing pin is built into each cartridge and is not part of the firing mechanism of the weapon itself. The overall function of the pinfire cartridge is identical to a rimfire, centerfire and I suppose other "patent ignition" systems.
I don't see why an obstruction in the bore, which in a revolver, by the way, seldom causes damage to the shooter, but rather only to the barrel, and only then if a round is fired with the obstruction in the bore, would be any more damaging or dangerous with a pinfire system than with any other conventional firearms.
The first reason for an obstruction in a bore, a cleaning patch stuck there, a wad stuck there (in a shotgun), a bullet sxtuck there, generally does no damage at all. It is the retardation of the gas behind the next bullet fired that causes bores to bulge occasionally splitting a barrel.
The damage occurs behind the second bullet, not where the second bullet strikes the firest obsturction from the rear.
The only part that the "force of the hammer" plays is that it must hit the firing pin hard enough to ignite the internal primer, the same as with any other firing pin system. The force of the hammer itself plays no part at all in the expulsion of the bullet from the firearm, other than what was said - simply igniting the primer. It is the primer that ignites the powder charge in a pinfire, and the powder charge that propels the projectile, as with any other system involving a more or less convention cartridge.
I have probably explained that just about as clear as mud. There can be other factors involved, such as very, very bad condition of the firearm, etc., but the above is basic.