denster:
Thank you for sharing your knowledge of common methods of orienting drum and nipple breeching. However, you are in error ("Powder chambers or connecting holes were not drilled from the front with a long drill, that just didn't happen.") as to CVA breeching method. While I'm not certain, I am pretty sure Traditions percussion barrels are made by this method (same barrel maker)
After the blank drum is threaded into the breech, the connecting hole is drilled (with a special piloted drill) and the nipple mortise is drilled and threaded using a jig to insure alignment with the hammer face. Of course, most gunsmiths and custom muzzle loading gun builders don't do it this way. When replacing drums on well used percussing guns I fit a blank drum as well. Once I get it properly mated to the barrel so it does not protrude into the breech I drill and thread the nipple hole at the proper angle to the hammer face. Track of the Wolf sells blank drums and the tools necessary to do this right.