A percussion hammer has a flat face to strike the percussion cap which is sitting on a hollow nipple. The flat face of the hammer
Do percussion hammers work well on center fire cartridges where the cylinders do not have firing pins incorporated for each chamber?
OK, bear with me.
In this photo, the percussion cylinder that originally came with my old EuroArms 1858 Remington is on the left, and the R&D 45 Colt conversion cylinder is on the right. Notice the percussion nipples in the the old Cap & Ball cylinder on the left. The R&D cylinder has a separate cap set onto its cylinder and there is a separate firing pin for each chamber.
Here is the hammer of the 1858 EuroArms Remington.
Here is the business end of the 1858 hammer. The vertical flat is what would strike the percussion cap seated on a nipple. The pointed part above the vertical flat is there to prevent cap fragments from flying out.
There is a groove milled through the frame so the hammer flat can strike the cap on the nipple.
With the cartridge conversion cylinder in place of the C&B cylinder, the same flat of the hammer is able to strike a firing pin mounted in the cap of the cylinder.
With the conversion cylinders made by Kirst, there is a fixed plate mounted in the frame that contains a single firing pin. The 1858 hammer strikes that firing pin no different than with my six shot cylinder.
That is the story with the modern conversion cylinders. They are designed so that they can be substituted for the C&B cylinder and struck by the hammer with out any modification to the hammer.
This is a photo out of R. Bruce McDowell's masterful book,
A Study of Colt Conversions and Other Percussion Revolvers. I hope that by giving full credit to Mr McDowell I will avoid any copyright issues. The hammer on this revolver has been altered to fire centerfire cartridges. A firing pin has been fashioned where the flat surface used to be on the percussion hammer and the overhanging lip at the top has been removed. Perhaps new material was welded onto the hammer to fabricate the firing pin, I am not sure. Anyway, it should be clear from this photo that once this hammer was in place, the revolver could never be fired as a percussion revolver again. We can also see the percussion nipples have been cut off of the cylinder, and a disc of metal has been added to the frame to keep the cartridges in position. When Remington converted their 44 caliber 1858 revolvers to fire cartridges, the cartridge was a 46 caliber rimfire cartridge. In that case the firing pin was at the top of the hammer, so it would strike the rim of the cartridge.
Another photo from Mr McDowell's book showing hammers for the Colt Richards Mason conversions, showing two different types of firing pins added to the hammers. Note that the hammer on the left has the firing pin riveted in place. Again, once these hammers were in place, the gun could no longer be fired with a percussion cylinder.
A few photos of an original Colt Richards Conversion.Here it is disassembled. Take particular note of the shape of the hammer.
Here a Pietta 1860 Army cylinder is on the left, the Richards Conversion cylinder is on the right. The nipples have been cut off the conversion cylinder and a new set of ratchet teeth have been formed from the center of the cylinder. Those are a couple of original 44 Colt cartridges in the chambers.
The Richardson Conversions had a Conversion Ring with a loading gate screwed into the frame, taking up the space where the nipples would have been on a C&B revolver. Notice the nose of the hammer has been cut back.
On the Richards Conversion there was a spring loaded firing pin mounted in the Conversion Ring. Not a whole lot different than the frame mounted firing pins of a modern Ruger.
Again, once it had been converted to fire cartridges, the Richards Conversion could no longer be fired as a Cap & Ball revolver.