RR, congratulatiopns on the new rifle. If you keep it clean and oiled it will give you many years of accurate use. However, as driftrider said, I would stay away from any surplus military ammo. I read a very good article in one of the gun magazines about the differences between military 5.56 ammo and civilian .223 ammo. There are some differences (I believe in the headspace tolerances that military ammo is held to) which could lead to a dangerous pressure level. So my best advice is to stick with brand-name civilian ammo and you should be very happy. For top accuracy try Federals Gold Medal Match ammo. It is pretty expensive compared to everything else, but it is what the custom gun makers use to test their guns, so you know it is good. For ammo that is almost as good but not as expensive try Black Hills or Georgia Arms. I personally use Georgia Arms stuff and I love it. Very high quality and affordable.
Best of luck.