I finish ream all of the chambers on my rifle barrels by hand. The barrel is set up in a lathe which is set to turn at its' lowest speed. Use cutting oil on the reamer and feed the reamer in to a depth of 0.100 inches per pass. Turn off the lathe, pull the reamer out and clean off the cutting chips. Re-oil the reamer and turn on the lathe and re-insert the reamer and cut another 0.100 inches. Use a live reamer made by JGS.
Repeat as necessary until you have done about 14 or 15 passes for a depth of 1.400 inches to 1.500 inches. Then take a headspace measurement using the barrel extension and the bolt assembly. Remove the BE and bolt and ream say 0.050 inches per pass and check HS after every pass. You will be close so go very slowly and check HS often.
When chamber is to final depth clean thoroughly to remove all chips and using a piece of 220 wet or dry wrapped around a piece of wooden dowel with the lathe turning slowly lightly polish the chamber. Repeat with 320 and 400 wet or dry paper. Chamber should now be done.
It really is better if you can have some one demo this for you as there are many small steps that are not easy to describe. Good luck. Charles the Gunsmith.