M1 Carbine Herlo Barrel

[byronroland]

Have to add, a muzzel wear gauge checks this brand new barrel at "1". I "think" this is fair as the tolerance is .300 + .002. I do not know how accurate the gauges are, mine is a Fulton and new (used 4 times).

Does anyone know what the design parameters of the gauges? Anyone have a print? We all know a .300 pin will not enter a .300 hole, if a .2999 pin does it is tight depending on roundness and such. When I measure the gauge (bought 2 just to check them out-one to the other). They are about the same. I have to assume the gauges are screw machined off with the body large and the groves cut, then ground at a taper from end to end? One of mine is out of round by a few thenths or less. I am going to check it out using ring gauges just to check what it is doing. I do not have here at my house, have to visit a grind shop to have access to more accurate tools.

Like I said, I am new and just learning.

Information

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[purple]

I have a finishing reamer inbound to set up the headspace on my new non-chrome Herlo bbl. Based on my Garand re-barreling experience, I prefer to use the pull-thru reamer after the barrel is installed, however pull-thrus are not available for the .30 carbine at present.
I'm going to use a technique to hand ream the chamber off receiver as described on this board by Gus Fisher. This involves the following:
-with the barrel at a hand tight position of 45 deg off TDC (mine is 40 deg), remove the bbl and ream the chamber to a point where the bolt will begin to close on the "no-go" gauge
-when the barrel is then installed and torqued to TDC the headspace will be correct on both the "go" and "no-go" gauges