I am trying to figure out the best way to build a proper full scale steel replica 1857 12 pounder. I have enough experience with cast iron to not want to go with a cast gun with a liner, so I am either going to use 12" OD 4.5" ID 1026 steel DOM seamless hot formed tubing opened up to 4.62" with a portable boring head and with a shrunk/welded plug, or a piece of solid 12" OD 1018 and bore it out. I can gun drill the blank to 1.25" full depth and then use that hole as a "guide" to incrementally open it up. Anyone have a good picture of a classic style blind boring head? I have one in a book somewhere but it seems to have gotten legs and walked off.