Basically, the K31 falls into two distinct eras - pre-1944 and post-1944. MOST, but not all pre'44 have a walnut stock. MOST post-44 have a beechwood stock. Because of the Swiss cleaning regime of using GREASE and not OIL [see the gazillions of posts on this subject, some ongoing right now] most K31 will have a bore that looks unfired. This is due not only to the method of cleaning, but also to the very high quality of the material used in the barrels.
Because many Swiss troops wore boot crampons, even while carrying out rifle drill, many K31 will have damaged ends to the buttstock - the Swiss also stacked their K31 in triangular 'piles' - that's what that funny-lookin' hookey thing is for underneath the muzzle - in the snow, and it snows a LOT in Switzerland. The damage can be healed to a certain extent, but at least you'll know when you look down that bore that the bit that matters, mattered.
One point to look for - SOME of the K31 made in 1944 had a reduced-quality steel used in the manufacture of the operating rod, that are somewhat prone to breaking off the little lug that engages in the cam track on the bolt. Replacements are available ror around $35-40, so check yours out for date by looking at Swissrifles.com.
BTW, not only the K31 shoots GP11, but every K11, G11 too - it was designed for them and they were modifed for it.
Graf and Prvi Partizan supply brass, in fact, the Graf stuff is made by PPU. It is Boxer-primed and very long-lasting. I have five hundred such cases in circulation, since I only need a hundred ata time, and they've lasted me for years. PPU also make a 174gr .308" bullet which is OK for plinking, and all the other bullet makers have a similar bullet in their sales list. Beware, though, that the original bullet was far ahead of its time, and you will rarely, if ever, make a load as good - Lord knows I've been trying for years without success.
Swiss Products in Montana [mornin', Lat] make a range of useful accessories - a clamp-on no-drill scope mount, a clamp-on muzzle brake, a clamp-on OR screw-on barrel harmoniser, a no-drill bipod mount and a set of exquisite diopter sights. I think that Trade-ex is the Canadian dealer, but Carlos here can put me right on that score.
If you join the rest of us over on
www.swissrifles.com, you'll be joining the very best Swiss shooting site on the internet, with thousands of pages of information, history, lore and advice on all kinds of Swiss firearms, military and otherwise. One of the most interesting facets of our Swiss guns is the necessity for the soldier to put his military details and home address on a plasticised paper tag, located under the butt-plate. Many owners have traced the previous owners or their relatives, and some great correspondence has resulted over the years. Again it is here that swissrifles.com is your friend, as we have a set of downloadable letters in the tree common languages for you to fill out and mail off.
tac
PS - note that the GP11 round has a performance about 90% of a .30-06 - kicks the same, too. That 174gr bullet is making around 2650fps or thereabouts, so taking game that you would normally use any .308Win or .30-06 - with a suitable hunting bullet - is entirely practical.