Harry,
Thanks. Glad you liked it. I've tried verbal descriptions, but they seem to fall flat. It's hard enough to see it even with the pictures.
Kingudaroad,
The consistent case problem is real. It usually adds no more than a couple or three thousandths in a batch loads with same-history cases. But if you start mixing your brass or it doesn't all have the same load history, differences in material distribution or in work hardening will result in differences in spring-back of the cases coming out of the sizing die. I would speculate that if you don't have a rigid press or you don't have every case lubricated identically, those factors will add variation as well, but I haven't done any experiments to validate that. If your sizing die isn't in exactly the same position in the press threads from one reloading session to the next, it will obviously shift the effective seating depth off the throat. Obviously a die that gets loose during resizing could cause a serious variation.
I think the RCBS Precision Mic is a worthwhile investment to check on case shoulder position or to sort brass after sizing so that you only take identical stuff to a match. I don't use its bullet seating depth feature because I find it tricky to their cartridge-shaped gauge without incurring position shift, plus the contour of their "bullet" doesn't exactly match the contours of my actual bullets, so the Stoney Point get the nod for that part of the job. I've considered grinding open the hole in the base of the Precision Mic to let it slide over the Stoney Point tool, but the latter is too large for that to work with caseheads much smaller than the .308's.
However, if you are benchrest shooting all with one lot of brass with identical histories to all cases, the problem goes away if you neck size only. Then the headspace is locked-in to your rifle and the standard gauge is fine.
Brselman,
How much accuracy effect you see depends on the individual gun. Seating depth seems to be yet another item that some guns are affected by significantly and that others seem indifferent to. Most prefer a bullet closer to the lands, but not all. The only way you will find out is to try it. Try giving
this link a read for an interesting tale about an old Mauser with a worn-out throat shooting one-holers.
Nick