The Gritters method is done in the headstock so I’m not sure what you mean..
In general it’s either Between Centers method or the Gritters method - Add one if you know of another.
Sir, evidently you haven't observed much chambering. The Gordy method is a way to indicate a bore when chambering. I chamber in the headstock and don't use or care for the Gordy method. You don't chamber between centers either. You can't get a reamer in a barrel with a center in it. You can machine just behind the proposed tenon to put the steady rest so you can then thread and chamber.
If you are a member (free) you can read this PDF about chambering and add to your knowledge.
http://forum.accurateshooter.com/threads/130-page-pdf-of-different-chambering-methods.3912170/
