Headspace gauges are your friend. It’s possible that the smith who chambered it didn’t sufficiently allow for the “crush” of tightening the barrel (which seems to be around .003” on most rifles). I’ve done it and had to deepen the chamber a hair. On hunting rifles, I’ve gravitated toward a slightly more generous headspace since reliability is paramount.
A gauge would rule this out as the source of your problem. Remove the ejector and firing pin assembly, clean the chamber and see if the bolt will drop with the “go” gauge inserted.
I would agree with the above. Headspace should also be checked after chambering, this will allow for the elastic stretching of the threads which can account for .002-.003 tightening up.
Winchester brass runs on the smallish side to begin with.
European brass runs larger in the Web, and usually use a CIP designed reamer vs SAAMI to avoid problems.
