the un-used calibers of surplus (8mm,7.62x54R,7.62x25TT,.303 british) (just to name a few) are extremly hard to come by these days as surplus and if you find some the ammo isint dirt cheap anymore....you can sometimes ifnd old surplus at gunshows as well....
i would reccomend buying new factory ammo and saving your brass and then getting into reloading....