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:
.22-250 Remington
.240 Weatherby Magnum
.243 Winchester
6mm Remington
6mm Bench Rest
.25-06 Remington
.250 Savage
.257 Roberts
.257 Roberts Improved
.260 Remington
6.5-06
6.5-284 Norma
6.5x57 Mauser
.270 Winchester
.280 Remington
.284 Winchester
7mm Bench Rest Remington
7mm-08 Remington
7x57mm Mauser
7x64 Brenneke
.30-06 Springfield
.300 Savage
.308 Winchester
7.65x53 Belgian Mauser
8mm-06
8x57mm Mauser
.338-06
.35 Whelen
.358 Winchester
.400 CorBon
.38 Casull
.45ACP
.45GAP