Question on barrel replacement ...

[Ron Wood]

G.T.
A half turn out (180 degrees) seems a bit much for hard hand tightening. I would expect about a a quarter turn for hard hand tightening and about the width of the extractor groove if you are using a wrench just before the final “ugh” crank on the wrench. As you probably know already, the torque of the barrel is an “interference” or “crush” fit. Looking at the original specification drawings you can see that there is a 0.1mm taper, or dish, on the rear barrel flange that allows for a final torque for this crush fit. Naturally, the final fit may vary from one gun to the next (but in actual production, this was usually a very small and insignificant variance), so if your replacement original barrel bottoms out too soon, you may have to remove a tiny amount (I don’t do thousandths well) from the rear of the flange to get the barrel to properly index. You might have to recheck headspace, but I doubt it.
Best to you backatcha,
Ron

[sheepherder]

Originally Posted by Ron Wood

...you may have to remove a tiny amount (I don’t do thousandths well) from the rear of the flange to get the barrel to properly index...

1 turn is .050" (20tpi = .050" per thread), so your 180º = .025"...but you want to leave ~ 1/8 turn (~.003"); so you'd want to turn off ~.022"...and that should leave you an extractor width away when hand tight...

.022" will likely require you to ream the chamber a bit...

Caveat: Measure three times, cut once...