I'm shooting a wildcat 300 NM 40Â° Improved and have pressure cropping up when I shoot brass that has been shot 3 times. It is a .338 neck and I turn brass to .336 for the initial firing. I then resize and head back to the turner to "clean up" the necks and leave it at the previous dimension. I barely remove any material on the second turning. What I THINK is happening is the brass is initially fired and the shoulder does not FULLY form. I fire the second time and the brass now has it's final shape but on the third firing, the same load that I fired the second time shows pressure with a shiney head stamp. I have no ejector so I can't look for that mark on the case head. When I measure the diameter at the neck/shoulder junction, I get 0.337 - 0.3375" with a bullet seated. Before seating, I get 0.334" after sizing in Neil Jones dies. The boat tail is being seated below the neck/shoulder junction. I use a 21st century neck lathe to turn the necks. Is there any way I can get an oversized expander and mandrel and force the donut to the outside and cut it off with out having to ream the inside of the necks? I'd like to keep my current dimensions and neck tension. Thanks.