Now I have noticed the old surplus ammo is cheaper, but also have heard it is corrosive and damages the bolt, firing pin and barrel. Is this true or is this hype to buy more expensive ammo? I'm old fashioned I believe that if the factory used it than its fine. Just like in a car sometimes when the factory says to use something and you try to upgrade it problems can occur. But if they are corrosive can I prevent this with oils and lubricating or just by cleaning?