Capgun cylinder - all you need to do is ream depth a little over half the ball diameter - pointless taking more out - we dont need more powder capacity, just need to be able to load a correct size ball. I did a army colt and a walker last year. I have a lathe, drill press, mill, I made the reamer from a spare bolt - but I did the reaming slow and easy by hand - used a T shape tap wrench to hold and turn the reamer - not so hard - and you can stop before you wreck the cylinder rather than after if you use the machines.
I went .462 we got a .464 pedersoli mold both guns shoot nice groups with full cylinder - never used to happen before. I didnt think it was difficult - maybe I am a competent machinist and dont realise it