VIS relief cut performed. Vertical Impact Surface. Where the back of the barrel lower lug contacts the frame. If the lower portion of the lug feet hit the frame breakage is possible. The idea is to make a relief cut, which leaves a bowtie shaped area at the top. This puts the impact area at the strongest point of the lower lug, at the top towards the tube of the barrel.
Mine had obvious impact marks and basically no relief cut made. It was atleast hitting even, but I don't want a barrel failure down the road.
I used a 7/16" long end mill with a .050 radius. EGW sells a cutter specifically for this as well, there's is a slightly larger diameter cut. Mine worked fine, it covers the area that needed relief. The cut does not take off much, maybe around .005".
Before
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In process
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After
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Smooth, DOGG !