OOPS forget my fist reply to Mikee Loxxer. I was thinking off the top of my head without my notes and put some wrong numbers. I will get the correct numbers and reply again.
What I meant to say was Trimmed Case Length should be 2.179 max. and 2.175 min.
The Overall Allowable Length is what is so variable in the K31. The Lee book shows and OAL of 3.051, while other sources say 3.006 or 2.948 but it all boils down to the bullet you are loading. If you are experimenting with lots of different bullet weights and manufacturers you will probably have to find your own OAL for each bullet type. This is where smoking a properly sized, trimmed and primerless cartridge and bullet will help find a sweet spot for each bullet type. I apologize for sounding like an idiot in my first reply to your question. That happens sometimes when you get old and don't have your notes in front of you. Sooooooo, to help make it up to you I'm gonna give you a couple of loads that shoot pretty well in my K31
Hunting load; Nosler 150 grain Ballistic tip, 41.5 grains of Hodgen 4895 and a CCI 200 primer.
Match load; Hornady 168 Boat Tail Hollow Point Match, 40.6 Hodgen 4895 and a CCI primer.
The K31 is a very accurate rifle and if you tinker with your loads you will be amazed how well it will shoot.
There is a guy named Pierre St. Marie who has a lot of really sound information online about the K31, you can either google him and get his site or get to it through
www.swissrifles.com. Happy shooting.