Hi
i bought a shaw rebarrel kit to swap the barrel in my savage 12 as it is at end of life. I understand how to swap the barrel and check headspace with the go and nogo Gage's. However I was wondering about two items.

first is the clearance from the bolt face to the front of the barrel. Is here a spec for this measurement? I recognize it would not be adjustable without cutting back the barrel or reaming and polishing the chamber, but wanted to check.

secondly what is the reason savage recommends to keep bolts matched to the gun? I am assuming it is headspace differences between rifles, but wanted to make sure.

thanks in advance!