Don't fret about the ammo. Prvi Partizan and Fiocchi make ammo for just about anything. Do get a reloading setup and you can recycle your brass forever. The K31 surplus ammo is outstanding, clean, but Berdan primed.
I just picked up a nice K31 at the pawn shop, ordered some Prvi ammo, I'll shoot it up and have 500 cases fire-formed to the rifle chamber to reload for a long, long time. The Swedish 6.5mm is at most shops. The 7.62x64R is either the cheap non-reloadable surplus or you can get the Sellier & Belloit or Prvi commercial stuff and reload it.