This got me wondering about something. I've watched some upper assembly videos lately, and they've all checked headspace after mounting the barrel. I've even seen it in all the written barrel-mounting instructions I've read that discuss headspace. But if you're planning to mount a barrel to a receiver, why wait until after you've mounted it to check the headspace? Isn't the upper receiver itself irrelevant to headspace?
Instead, couldn't you hold the unmounted barrel vertically, drop in your headspace gauge, insert your bolt (without ejector and extractor), and see whether you can turn it or not? After all, when using a field gauge on a mounted barrel, the carrier is supposed to stick out behind the receiver because the bolt can't turn in the barrel extension, right?
I'm just thinking how I'd hate to go through all the barrel mounting procedures before discovering the barrel was out of spec. A lot of guys buy parts over a long period, and to discover your barrel is out-of-spec several months after you bought it might cause some problems if you need a replacement.



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