[pilgrim
With the dimensions you have provided,your drilling seems to be either one or the other of two different cartridges.The marks 7.8/57 could be either 8x57IR or 8x57R/360. Go back to the chamber cast and measure the diameter just ahead of the rim. If this diameter is near .468-473", then it is 8x57IR. If it is near .427-433",then it is 8x57R/360.If the dimensions for barrel groove/land diameter are correct(depends on material for chamber cast and time after casting the measurements were made)then standard 8mm .323"bullets are useable,in fact, if 8x57IR then 8x57IRS is likely to be useable.More often than you would think,8x57IRS is useable in 8x57IR chambers.There are differing opinions of the reason for this. A 8x57IRS chambered rifle would have been marked 7.9 or 7.92/57- This is just one of those differing opinions.
Mike
