Forget all of this fancy $hit and buy an "ugly old AK47". The commie rifle is plenty accurate out to 200m and is fun to shoot. The mags(30rnd) are cheap, readily available and will last forever. Ammo is still less than 15cts per round. These rifles DO NOT JAM! They will not let you down.
I'm an M1-A .308 guy (20 rnd mags).
Mil surplus 7.62x39 is about half the price you quote. I think now you can get 1000 rounds for about $80.