I am having some trouble getting the aluminum gas checks to seat square with my Lee push through sizer. Checking these onto .225-sized bullets. Using .008" aluminum.
Does not work at all pushing through nose up, so I push the bullets through check-first/nose down. It crimps them on tightly enough, but they are often not square; if it's square, it luck of the draw.
I suspect that the problem is that the inside diameter of the check is big for the shank, so the periphery of the check is not supported as it gets formed around the shank.
Think this might be remedied by using a little thicker aluminum to reduce the gap? I guess I will try it.