Adventures with with breeching washers

[boatbod]

I had the day off today and wanted to occupy myself with something other than a honey-do chore. Luckily I was the only one home, so I was able to spend the day in my shop fiddling with machine tools and guns.

Anyone who has followed my other thread and the saga of the sticky chamber will know that despite my best efforts, I have decided to replace the barrel on my .308 M1. Aside from these extraction/short stroking issues, one of the other significant problems is that the barrel is barely hand tight when correctly indexed in the receiver. At the time, I proposed to fix this by making a breeching washer and cutting back the shoulder. With nothing to loose except time, I figured I'd give it a go.

First I turned a piece of steel down to 1.10" dia to match the barrel's OD, then I bored it to 0.970" to be a nice snug fit over the threads and tenon. After that, I parted it off with a nice sharp tool to leave a finished thickness of 0.090", and smoothed away the burrs on a diamond stone.

Next I chucked the stripped barrel in the 4-jaw and cut the shoulder back by about 0.085" as a starting point. Although I've only got a smallish (10" swing) lathe, I was able to screw the receiver onto the barrel with it still in the chuck so I could take a succession of light cuts and test fits to get the receiver + washer to come up hand tight around 4:30.

The barrel and breech washer were then cleaned and blued before final assembly using the ubiquitous barrel vise and receiver wrench.

Headspace tested out just fine - the bolt still doesn't fully close on a .308 NOGO gauge, and although the right hand locking lug is a touch further rotated than before, there is about a 3/16" gap between it and the receiver rail. A FIELD gauge obviously comes nowhere close to closing.

If I were to go through this again, I'd target the 5:00 position for hand tight. It was a real effort getting the last few degrees rotation using a 12" receiver wrench handle, and I thought I was going to need to find a breaker bar to help things along.
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