I might add that the block and hammer pivot on cross pins of large diameter. Replacing these pins with shedule 8 bolts is a standard job a friend of mine does on black powder rolling block actions, as the issue pins are quite soft. These pivot pins stick just through holes in the side of the action, taking all of the shock and pressure of firing.
: Modern made Italian replicas by Pedersoli have been checked to very high pressures, but typically, they have firing pin's of large size preventing anything over about 30,000psi loads, even in the newer actions. With firing pins bushed, higher pressures could possibly be used. Note, I said possibly. Val Forget of Navy Arms apparenly tested one (many years ago) to 50,000psi and it held up just fine. I would not suggest anyone else doing the same.