Re: Semi tight neck chamber?
As long as the necks dont expand more than .005" at firing your OK. I run a .315" neck on my 7mm reamers, 7/300wsm, 7wsm, 280AI, 7-08, 7mmRM etc. If the necks do expand more than .005" at firing when you size the brass down, run out in your sized necks will be present.
If your running a loaded neck thats .310", a chamber/reamer neck of .315" would be fine. I'd use a .308" bushing to start.