The MR762 is chambered in 7.62 x 51 and will safely shoot such caliber amunition manufactured to SAAMI specification with a max chamber pressure of 50,000 PSI.
If you shoot .308 WIN which has a max allowable chamber pressure of 62,000 PSI you could run into trouble if your .308 WIN round is loaded that hot.
So to answer your question more directly, YES, 7.62 NATO ammunition is safe to shoot in your MR762.
.308 WIN however must not contain a payload which will exceed 50,000 PSI chamber pressure.