Conratulations! You will
love this rifle, (until you take the bolt apart and try to put it back together the first time without help!)
I don't think the 7.5x55 cartridge was ever loaded corrosive.
Surplus Swiss GP11 Military ammo is great stuff, but not real cheap, and it is not easily reloadable because it has Berdan Primers. Save the brass anyway; it CAN be reloaded in a pinch, but it is a bit of a pain.
I think Hornady is now loading up new Boxer-primed factory ammo , but I haven't shot mine in so long, I'm really not up to speed on the ammo situation.
I mostly sized and loaded .284 Winchester brass for mine.