I've owned both the K-31 (still have three in fact) and the Mosin; 91/30's and an M39. Absolutely no comparison in my experience. Even unaltered some of the K-31's that have passed through my hands are more accurate than some of my production scoped centerfire bolt rifles.
Some 100 yd. targets from unaltered K-31's:
1940 Model with jacketed handloads:
1943 Model with jacketed handloads:
...with GP-11 surplus ammo:
1939 Model with jacketed handloads:
Now for the "worked over" K-31, a '53 model. I did some work on this one so I could use it in our local High Power matches. Bedded it, worked on the trigger and most importantly, put some sights on it that I could see. In retrospect, the bedding was probably unnecessary. Be that as it may, the rifle is extremely accurate and capable of much more than I. Initially I mounted a cheap Williams peep sight on it and left the original front sight:
With a jacketed handload:
With GP-11:
With cast bullets:
I later mounted a Lyman 48 then finally found a way to mount a Redfiled Palma sight on the rear and Lyman 17 on the front:
I shoot 99% cast out of this rifle and she's embarrased more than one AR competitor at our High Power matches.
Part of the beauty of these rifles is the fact that the surplus Swiss ammuntion is amazingly accurate, easily rivaling my most carefully assembled handloads, and at a little over 50¢ per round, it's relatively inexpensive.
35W