Gas check seating difficulty

[DrDucati]

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.

[DrDucati]

Did some measurements. It's actually the opposite. Although the diam of the check-forming punch is the same size as the shank, using alum thicker than .004 results in a check with a radius/bevel on the base. This is why they are so difficult to seat square.

It's the design of the check maker in .223 caliber. I think the forming cup and punch are small relative to the thickness of the material. The inside diameter of checks made with pop can aluminum is shank size all the way to the base, and they seat very well at .004" but that aluminum is too thin. 0.213 shank + 0.004 (x2) = 0.221", and they will seat square but a .223 or larger sizer won't crimp them tightly to the shank. To use thicker aluminum for a good crimp and have them seat square, I need a larger forming cup and punch. When I switch to the larger plain-base-check-sized forming cup and punch, I get a larger inside diameter at the base of my checks with the thicker aluminum. So they fit better.

Maybe that will help someone who is crazy enough to make checks for their .223".

[Shiloh]

I have a method for a lubrisizer, but not a push through. I never installed a gas check with a LEE push through sizer.

Shiloh