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.
FITS: .22 Savage High Power, .25-35 Winchester, 6.5mmx55 Swedish Mauser, 7-30 Waters, .307 Winchester, .308 Marlin Express, .30-30 Winchester, 7.5mm x 54 French MAS, 7.5mm x 55 Schmidt-Rubin, .32 Winchester Special, .32-40 Winchester, .356 Winchester, .375 Winchester, .38-55 Winchester & Ballar