Maineshops,
I just finished routing out a 42" "B" weight swamped barrel channel on an old round ram bridgeport. If you have access to CNC machine with sufficient travel it would be pretty straightforward. The machine I used was manual and had a total x travel of 18" so I had to move things around quite a bit. I held it in a pair of vises. If you are doing a straight barrel it would fairly simple, but the swamp increases the number of set ups significantly. If paying someone to do your barrel channel and ramrod channel and hole is an option, I would suggest it. If you want to do it just for the experience, private message me and I will give you my phone number to discuss it. To cover the whole process of work shifting and machine manipulation to get this accomplished I would have to write a short book.
Blessings, Bill