Re: Free Recoil Zero Shift
For me, Free Recoil = only touching the gun with the right (trigger) hand and the left hand goes on, or in front of, the rear bag. Medium to light grip (trying to be consistent) on the part of the stock behind the trigger. All of my rifles have vertical style grips (McMillan A-5 on this particular rifle). Not pulling the rifle into my shoulder with much, or any force, but nonetheless the rifle butt is somewhat solid on my shoulder as I am leaning into the butt of the rifle.
By a 'firm hold' I mean holding the forearm of the rifle just behind the front bag with a moderate downward pull on the stock, trying to be as consistent as possible. The trigger hand is pretty much the same as with the free recoil hold, but the rifle stock may be pulled into the shoulder slightly harder than with free recoil.
For me, it feels like I have a hard time being consistent with the 'firm hold' as the degree to which my left elbow bends varies based on what elevation (angle) I am shooting, whether I am shooting prone or at a bench, or even between the different benches at the range. In some cases the bend angle in my left elbow feels very ackward and it is a struggle to keep a straight downward pull on the forearm.
As far as field positions go, I try to practice those also. Before the rebarrel and brake, my rifle shot almost exactly 1 moa high off of the Stoney Point tripod sticks. I could not detect a significant zero shift shooting off hand, sitting, or kneeling (at least withing the variation of my wobbling in these positions).