I have a savage barrel and want to install it and head space it for the 243 AI (it is chambered 243 AI).
Can I use the Go gauge for a 243 WIN? I have a go, and a no go in 243 win.
Or, should I just fight fit against a fired case?
It should be a snug fit on a new case.
The GO for the WIN becomes the NO-GO for the AI - if it closes on it, it will have too much headspace.
I'd probably set it off a virgin .243 brass.
John
You don't need a gauge, a case will be fine. I'd always start with new brass for an AI, but did by mistake use some once fired and came out ok. With once-fired, screw the barrel in to where it's up against the case, then back off the bolt and go another 1/8 turn...about .006". New brass can vary quite a bit - I've measured .009" difference headspace between the longest of one headstamp to the shortest of another. With new brass I'd grab a handful of cases and with the barrel screwed in chamber each, then use the one that headspaced shortest and do the same thing (back off the bolt), then screw the barrel in another 1/4 turn - .0125".