Well I did some searching for gas checks for my Accurate 200 Grain 10mm boolit. Some great advice but I like to keep things simple. So Imordered some Hornady .416 gas checks and sized the boolits with these and they worked out perfect. They seated even and symmetrical. So now I can get the rest sized lubed and GC crimped on and load up some 200 RFN GC hard cast for my numerous 10mm guns.