I have a couple K31s, too. Nice rifles. The G91 milsurp ammo is non corrosive berdan primed. Great ammo, nice brass and reasonably inexpensive but NOT reloadable with boxer primers. I use PRVI brass, rather ammo, then reload the brass. The PRVI ammo runs around $15-18 per 20. Grafs has two types of custom ammo, much more expensive, loaded by Hornady. They use PRVI brass as well.