There is an angled shelf just below the ejector that sometimes has forging material still on it. If it isn't locking up properly, it MAY be that excess material. My .357 barrel came from NEF, fitted to my receiver, and still failed to lock up properly. By smoothing the locking shelf, it locks up perfectly now.
Prussian blue would be a very good check, or the wear marks in the blueing would give a good indication of how deep and squarely the lock is moving. If the release isn't coming up high enough, I would normally suspect the shelf as part of the problem, not the hinge pin. Of course, the ejector could have some junk in it that keeps it partially open, that would cause the barrel clearance to be reduced.
The hinge pin and barrel socket for the hinge pin are areas that should never need messing with, unless the barrel won't even close. Tolerances are usually close enough, with modern techniques, so they can turn out endless barrels with the same pin to receiver dimensions. They are always machined for final fit after blueing. The locking shelf isn't touched after the initial forging and blueing.
I had a barrel the other day, on a "NM" SB2 receiver , that never did lock up properly (it popped open after every shot), even after smoothing the shelf. I ended up putting that barrel on a shotgun receiver that allowed it to lockup and took the .22 Hornet barrel that was on the shotgun receiver and put it on the "NM" receiver. Everything works perfectly now.
I would think leftoverdj would have more knowledge on this subject than I have. I'm just telling you what worked for me.
