Angus,
You must have a different definition of "waay" different.
The only differences between the 8x57 and 7x57 cases that would be obvious to the naked eye are the length the diameter of the neck (which is obvious from their names), and the length of case body from the head of the case to the rear of the shoulder, which is about .1 inch longer in the 8x57.
The diameter at the rear of the shoulder in both cases is within .001 of .43 inch/ The shoulder angles are both just about 20 degrees, and the overall case length differs by about .01.
No, the 7x57 is NOT exactly the 8x57 necked down, like the .270 Winchester is the .30-06 necked down. But the dimensions are so close any difference in powder room would be due to the heaviness of the brand of brass, not case dimensions.
