I wish I had a Swedish Mauser to compare to my K31s. I would suspect the longer barrelled M96 might have an edge, given comparable condition rifles. Also, 6.5mm is a ballistically superior bullet diameter if there is enough case capacity to achieve decent muzzle velocity. Not knowing anything about the 6.5x55 caliber or its case capacity, I would suspect the M96 would be my choice to start a 600+yd target build. The K31 was originally designed as a compromise between karabiner and standard rifle models. I think the K31 barrel is 24" or 26". I'm having a brain fart and can't remember at the moment. Doh!