I am getting caps blown off the nipples with 20 gr 3f in a .36. They aren't split (#11 caps), but just backed off and dropped into the curve of the hammer (1862 police). Neither are they extruded into the hammer slot. Could it be that the flash hole is too large? Anyone ever try to braize up a flash hole and re-drill a smaller one? Would slix shot nipples be an improvement? Only happens with a heavy load.
Can’t answer that, although I’d swap out the nipples and see what happens. If still blowing off caps, I’d look at a new spring. Suggest nipples first because they eventually get peened to the point they’re unreliable and have to be replaced and if that’s not the problem, you’ll have a spare set.