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Old 12-06-2017, 06:31 PM   #41
Curio & Relic
AKaholic #: 6541
Join Date: Sep 2006
Posts: 8,807

Originally Posted by OHVET View Post
Doesn't seem right to me to say a Go gauge should not completely close. I would think if a No Go was on the max acceptable measurement then the Go gauge would certainly be closing. And a field gauge is the ultimate limit and I am to believe a Go gauge is still not rotating completely?
The bolt is mechanically limited form hitting the trunion when the carrier is installed You want to check that the bolt can reach the maximum it can travel on a go gauge .

If your referring to rotating to a point were it hits the trunion then it is closed and past were it will be .

you want to check head space at the point were the bolt will be when its fired not some were it cant be .
the carrier prevents it from rotating past a certain point .

In the picture above its rotated past were it can go with a carrier involved .
from that point it can get slightly tighter due to the lugs being machined on a helix and the fact it will also rotate onto a unworn area of the trunion .

You can rotate it all the way like that and it ill still likely be fine but if you set it up really tight on the GO gauge at the rotated clear to the trunion position with certain gauges you may get close to a round may not chamber .
I think it gets around a .001" or less tighter on new parts . As I recall please don't quote me on that .

Keep in mind CIP and SAMMI gauges will be slightly different on the GO gauge a CIP can give a slightly tighter head space if you were to set up the gun snug on both .

I use a SAMMI gauge and I set it up snug with just a bolt .
the results should be the same with the carrier installed in what id call a final function check .

millions of rifles set up using the carrier method and 95% of the time or more it will work fine . I pointed out some personal examples of how it can fail . it takes maybe 5 minutes extra to use just the bolt first and then include the carrier and verify its the same . If its not it should be a big red flag.

Again check bolt , extractor to breach clearance before you ever install a barrel and if its already installed check it before you every check head space .
also make sure a round protruded about the same or slightly less than a NO go . this will verify that the neck and thorax is big enough to take a round .
I had a new barrel once that was short chambered and I had one once that the throat was to tight on . you should also check the carrier and bolt fit make sure is closes smoothly on a empty chamber if its tight that's sure the hell going to affect any pull gauge check . these are mechanical issues nt head space issues
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