Looking to purchase a first rifle. I saw army surplus ammo that is about half the price of 7.62x39 or .223 ammo. Kinda tempting. Anyone has experience with this type of ammo? I'm sure its probably corrosive, but good cleaning methods will do good. Not sure if I should go and buy a bulgarian ak-74 or smith & wesson's m&p15r. They are both not too far in price. Any thoughts?