CCCC,
Actually, according to some basic rules of internal ballistics, the 8x57 is capable of about 7% more velocity than the 7x57 when using bullets of the same weight, everything else being equal--which means the same pressure, the same barrel length, etc. This may not sound like much but amounts to around 200 fps in loads using 150 to 175/180 grain bullets.
Have published a lot of information on this subject, and other basic rules. In fact, a chapter on it titled "The Rules" has appeared in two of my previous books, and will also appear in the soon-to-appear GUN GACK 1V, THE LITTLE BOOK OF RIFLE LOADS THAT WORK--partly due to reader requesting it be reprinted again.
