Thanks Pard, I'm not sure but I would think the rim of your 7x57R would add a bit of weight. I'm also not sure of the 8x57 neck down. When comparing case capacity, I usually just weigh them first, and find the ones that are the heaviest & the lightest. After I size them, primer in, I fill to the case mouth with a fine ball powder and weight the charges of the two. Thats close enough for my uses. I have found some cases that are heavier, yet still close in capacity, depends on how the inside of the case head is made, etc. I am of the personal belief that if one does not have a :bonafide 1/4-1/2" 5 shot grouper rifle, some experiments are pointless. I do, however, stick with loads for one brand of brass. I keep them seperate, usually with a different bullet/purpose. I make good notes and just rezero for them if used for a hunt. Thank you sir!