Just picked up a Varm contour 1-8" 16.5" McGowen that was in stock from a place in VA. I was told that all you have to do with 221fb brass is just run it through a 300blk size die. Haven't tried it yet as there is 300blk brass available, and I have 500 LC 5.56 that I can convert before I spend money on 221fb.