Another "Red Herring " for you . I read a number of years ago about a long range match cartridge that was made by chambering a 6.5 X 55 four milameters short. This allowed the use of plentiful 308 match brass. A standard 6.5x55 die set was shortened to accomplish the reloading task. Very similar idea to the David Tubb 6mm cartridge.
A number of years ago, 40+, Boxer primed, 6.5x55 brass was next to impossible to find in Canada, unless you could find some of the old Dominion stuff or you wanted to pay outrageous prices for Norma ammo, which hardly anyone carried at the time.
There were other, readily available cases that could easily be resized with one pass through the 6.5x55 resizing die. 7x57, 8x57, 308 Win etc.
There was always lots of 308 Win brass around, everything from surplus IVI to several commercial types.
Sizing down the 7x57 and 8x57 wasn't really practical, because it was also on the scarce side, so I went with the 308 Win commercial if I had to but preferred the surplus IVI 7.62x51, especially the BLANK cases, which were seldom policed in the field.
I managed to collect a couple of thousand fired BLANK, IVI 7.62x51 cases and after cutting back the petals on the case mouths, ran them through the 6.5x55 sizing die, trimmed to proper length and fireformed them. The surplus cases had thicker webs than the commercial so when they expanded to fill the chamber, there was little chance they would separate later.
I think I still have some of those cases.
You have to do what you have to do.