Not that you will probably find it anymore, but I fired 7.62 NATO ADI ammo in mine when I had it. ADI is Australian, so technically it wasn't NATO ammo.......but you know what I mean. It was surplus 7.62x51 ammo with 147 grain FMJ if I remember right. It is great ammo. Still have some for my 2A Enfield.
You can get German and something else from different online vendors right now. I would steer you away from the Wolf 308 as it has been inconsistent and higher charged than other 7.62 ammo.
Like Quick says, you are better off with new, commercial ammo most of the time. If you can find it, the Remington UMC 308 was pretty good in my Handi if I remember right. Was awhile ago.
Looking online, AIM Surplus has South African for $60/140 round battlepack. Great ammo at .42 plus shipping. I figure that anything cheaper than .50 is a good buy right now.