Should have gone the M96 route, I believe. A friend has a ,93 which is barreled in .308Win. - I would not shoot it, personally.

If going ahead with this - I'd stick to 1940's era velocities, like 2,350fps with 173 to 175gr. bullets.

The .308 is a SAAMI 62,000PSI round.
The 7x57 has a CIP Max. of 57,000psi.

http://kwk.us/pressures.html