Quick question for those of you who run a switch barrel rifle,,,, as in week to week even

I'm in the process of putting together a 6.5 Lapua, varmit barrel, heavier stock, etc.

I have an additional stock I'm going to skeltonize, and am still looking for a 308 barrel, in somthing like 18 inches.

My plan all along was to just build the Lapua, but I have a wild hair I need to satisfy. Just wanted to see how light of a savage I can build, and also how the shorter barrel does over the chrono. That and it gives me a loaner rifle of sorts for the couple times I may need one in a year

Anyway, the plan, as it is in my head would be to bed action in both stocks,,,,allowing for the nut to be free floated as well, or at least not engaged into the wrench cut-outs.

My real question is headspace. I want to be able to put the barrel EXACTLY back into the same, no to little headspace condition each time. Say you had a little less or a little more headspace, all that fireforming and case prep would be lost.

Could I index using a scribed line? Some type of stop? Just wanted to poll to see what others are doing?

Thanks