This is the cam or pin that the tail of the bolt rides on located on the hammer of my 1851 Navy. The spring end of the bolt has cut it away to the point where the bolt would sometimes not disengage the cylinder at half cock. I probably have about 150-200 rounds fired. After each use the gun was stripped, cleaned, and lubed with Ballistol. Maybe at that contact point grease would be better? Today I did replace the hammer and bolt and was fortunate that the repair was simply drop in with no filing or fitting needed.