LRF,
The 7x57 case( including 7x57R) is based on the M93 case, which is .473" head diameter, instead of the M88 case( 8x57/8x57IR/IRS) which is .468"(both dims. max). Most European cases follow this, but American cases are usually made 06 size( incl. 6.5x55). You might keep this in mind if you intend to use European cases.
Mike