SAAMI sets the standards for USA produced stuff and CIP in Europe sets the standard for most European made stuff - is not random. 30-06 originally created by US military, like 20 years before SAAMI existed. 8x57JS was a German military round from about the same time - 1905 or so. If you are buying North American made ammo, it will be called "8 mm Mauser" - the name that SAAMI invented for that cartridge. Go here:
https://saami.org/wp-content/upload...99.4-CFR-Approved-2015-12-14-Posting-Copy.pdf That is the SAAMI standards for cartridges and chambers - 8x57 rim is 0.473" -.010" diameter; 30-06 is the same. Note on those pages that the top diagram is the cartridge; the lower diagram is the chamber. CIP standards will have the same dimensions, but much higher pressure rating for 8x57JS, compared to USA 8 mm Mauser - but the two are physically identical size and shape. You can see that SAAMI specs a slightly smaller rim diameter for 9.3x62 and slightly larger for 6.5x55, and so on - those are NOT the same as 30-06, but pretty close.
European companies like Prvi Partizan made 8x57JS for European market and 8mm Mauser for North America - same brass, same bullet - typical that the 8x57JS throws bullet circa 200 to 250 fps faster than 8 mm Mauser. Go here:
https://www.prvipartizan.com/rifle_ammo.php Note that when you select a cartridge, it shows the bullet part number among other things - and the velocity and barrel length that they used - compare 8x57 IS (in Europe, that "J" is often written as "I") to the 8 mm Mauser ammo that is sold in Canada and USA.
Go here to see a chart comparing USA SAAMI and European CIP pressure standards - note that both organizations have used TWO methods to measure and report pressure - not the same to each other, so need to compare CUP to CUP and PSI to PSI ratings.
http://kwk.us/pressures.html You can read in his notes toward bottom that is not any "official" entity's report - that guy has been gathering SAAMI and CIP pressures from various sources for years - put that all together on a chart for us to read and compare. I found some of his comments near the bottom to be fairly interesting.
Is not to say that every piece of brass made by anyone, ever, is going to fit those numbers - just will not be SAAMI (or CIP) compliant, if they do not. I am not aware of any military anywhere, that follows SAAMI standards - they set their own - often similar, but often not - so Swede's have set their own standards for 6.5x55 and produced it for like 30 years before SAAMI existed. Same with British and 303 British ammo. USA military was making and using 30-06 ammo long before SAAMI existed. I am sure there are many other examples.
