AGS The 8x57 and 7x57 were not made on the same head size cases, nor were the rimmed versions. The 8x57/I/IS/IR/and IRS were made on the M88 case head diameter of .468", whereas the 7x57/ R were made on the M93 case head diameter of .473"(The 30-06 is said to have been copied from the 7x57). It is possible that S&B made those 8x57R cases with the same draw dies as the 7x57R (M93). Modern manufactures often make ammo with case heads different diameter than original design. My brother had a 6.5x55 caliber rifle and was handloading with modern American cases (with correct headstamp), with .468" head diameter. Actual measurement of 30-06 and other 06 size cases often show head diameter of .468". This is all OK as long as they use the smaller size but can cause confusion if they use a larger size. We often talk about "tight chambers", and they do happen, but the problem can also be the ammunition rather than the chamber.
Mike
