This Remington pistol came into the shop with a broken firing pin. We ordered a replacement, but the diameter of the firing pin body was simply too large.
After disassembling the block, I simply center drilled the original firing pin body about .150" deep. Next, I silver soldered a .090" diameter piece of drill rod in place.
I made sure the new firing pin tip would clear the firing pin hole in the block.
Once the firing pin was in place, I trimmed the length while pushing the pin from the rear to ensure it was at maximum protrusion. Normally the protrusion is between .055" and .075" depending upon the firearm. With older antiques I leave them a bit longer. Age often comes with wear, and sometimes you have a bit of loose breech. Not enough to make it dangerous to shoot the firearm, but I like to make sure the firing pin can reach the primer. If the firing pin tip pierces the primer I can always shorten it a few thousandths of an inch.
Once the firing pin is given a flattened hemisphere shape, I reassemble the gun and test fire it. I make sure to check for pierced primers in the case.
.50 Remington is a short and squat pistol case. The breech opening is rather large compared to modern cartridges.