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Old February 19, 2013, 01:55 AM   #6
Join Date: August 23, 2006
Location: Los Angeles, CA
Posts: 53
300 win mag headspacing

Originally Posted by gmckinney626 View Post
Ok, so my first time doing a belted magnum. This is on a 700 .300 WM. I have the go and no-go gauges. I have a Shilen #8 that was threaded and deep chambered at Shilen. I have a thicker recoil lug to install, so obviously, the shoulder has to be set back. The belted gauges have me awefully confused. My concerns are as follows (I'll try to provide as much info as I can):

I'll have to face the barrel to remove the scribings, so I know to account for that with my measurements. I have installed the go gauge and screwed the barrel down onto the action to get a measurement of how far to set back the shoulder. I then removed the go and installed the no-go. Still screws down to the same measurement. As I understand belted magnums, they space off the belt. I've also tried screwing it down on the no-go until it won't close, but then it won't close on the go. I took my measurements on the rim to belt face on both and got .220 on the go and .227-8 on the no-go. The barrel isn't bottoming out on the receiver. So, if I'm getting the same measurement when it's screwed down on either gauge, what am I missing on the cutting that needs to be done?
Are you sure the barrel is not bottoming out on the bolt nose?

Start by screwing the barrel into the receiver with the bolt already locked in battery.
Look at where the barrel stops and measure the gap where the recoil lug would sit.
Run all your measurements against that.

Try out my barrel fitting worksheet to take all your critical measurements and then do your calculated measurements.
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