I would assume the way a big barrel manufacture would do it is, drill bore and then roller burnish the inside. I do this at work in steel and get a mirror finish. We hold +/- .015 mm roughly a thou total tolerance. An I do this on an okuma vmc. A lathe would produce a better result. If you wanted to bore the barrel with a freak insert, you would need to indicate the barrel on a 4 jaw chuck and bore it with a 5/8" boring bar. If you wanted an oring groove you would need to get a very long and small grooving tool. It wouldn't be hard at all, just time consuming. I wouldn't bother with an oring groove personally assuming you have a close fit on the insert.
Look up cosdil, their roller burnishers will make a better finish than a reamer and in less time than polishing. It basically presses the material outward with rollers and "work hardens" the bore. The prefinished bore would have to be undersized. I think we leave about .0006 and the burnisher presses material to size. They're amazingly expensive though. But so is anything in machining.
Last edited by RabidHobo : 03-31-2013 at 11:58 AM.