If your shell holder doesn't securely grip the sell and firmly fit into the press during reloading, you're bound to have headspace and sizing problems. RCBS manufactures their shell holders to the industry's tightest tolerances, using only the finest steel. #16 Shellholder fits: 30 Luger (7.65mm Luger) 30 Mauser (7.63mm Mauser) 9mm Luger 9mm Makarov 9mm x 21 9mm x 23 Winchester #17 Shellholder fits: 30 M1 Carbine 32 Auto (7.65mm Automatic)