Mickey

Did you use 7x57 factory ammo? If so you would have found the cartridge in factory form is under-loaded. To be able to be shot in old weaker falling block rifles in 7x57.

The 8x57 vs a .30-06 - it will have a slightly more curved trajectory as the 57mm case is smaller, but the .323 bullet has less friction than a .308 but of course also a lesser section density for the same bullet weight.

BUT for practical hunting purposes no difference.

For obvious reasons it is a popular round in Europe.