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
You are correct and the point I was making was that some of the 8x57 R is made with the .473 head. I checked some S&B 7x57R and it is .473, so again it wouldn't work to fireform. THis was a case where precision caused a problem. A little slop would have come in handy.
