It seems that when I shoot prone I very soon get a splitting headache. It gets really bad when when stand back up. I have raised comb height, tried 6" to 9" and 9 to 13 bipods, and changed the way I sit behind the rifle. I'm not old or seriously out of shape. I'm ok on a bench, sitting, kneeling, etc. I usually just tough it out until it gets bad enough to affect my eyes and shooting.This last time my neck muscles were stiff for a couple of days, so I started thinking maybe the muscles were just wimpy. I got some advice that I should relax a bit and relax between shots.I'm going to try and do that more often. I just thought I would see if any of the discerning shooters here have ever run across this issue before. It's quite annoying because im not really into shooting off the bench.