I think I've learned that:
If the bolt is late from being released by the hammer cam top flat surface, it can be corrected by filing vertical, a little bit off the end of the bolt leg. That would allow an earlier release of the bold.
From observing my Pietta Frontier, the bolt gets released right at the top of the cylinder notch ramp. Quite different compared to my Ruger Vaquero which releases the bolt right after it leaves the cylinder notch, leaving a nice long mark to the next notch though the timing is good when the trigger drops into the sear of the hammer. Needless to say, I'm very happy with my Pietta 1873. Fortunately being stainless, the mark easily rubs off with a little bit of Mother's Mag Alu polish.