M 1916 spanish Mauser.....

[vintage hunter]

.....Most do agree that Winchesters .308 is a fine enough substitute.....But use no others.....pressures are greater......

That's a crock. The SAAMI maximum chamber pressure limit for the 308 is 62,000 psi. Ammo makers, Winchester included, usually back off this a bit but most standard loads still average 58,000-59,000 psi.

Plenty of 7.62 NATO out there.

I wouldn't fire 7.62 NATO in it either. Contrary to popular belief chamber pressure is the same as commercial ammo.
The M1916 Spanish Mausers were chambered for the 7.62 CETME round. It's dimensionally identical externally to the 7.62 Nato/.308 but chamber pressures are only around 45,000psi. If you intend to shoot it use the appropriate surplus ammo or light handloads.