All new barrels are short chambered and require finish reaming in order to establish proper headspace. Of all the NOS GI barrels that I've installed I only found one that would accept the "go" gauge with a used GI bolt w/o any finish reaming. It is important that proper headspace is established on both the "go" and "no-go" gauges.
OK, so how would one deal with installing a Used barrel?
Grizz