If the numbers on the stock match the rest of the rifle, then it's been re-arsenaled/restocked. I've fired many, many hundreds of rounds through several K-31's, mostly in local High Power matches. They're so accurate, it's unbelievable. I've left many AR shooters in disbelief at matches.
Before you go on too much of a search for bullets, try the lowly Hornady 150 gr. FMJBT. They shot incredibly well in my K-31's. Here's a 100 yd. 12-shot groups fired with one of my K-31's and the Hornady bullets:
...and another from the same rifle with GP-11:
A group I fired from my cousin's K-31 with GP-11:
A group fired from a '40 model loaded with pull-down 152 gr. FMJ bullets:
I performed some modifications to a '53 model and it became my "match" rifle. Our local matches are on a reduced course, but I set up a 600 yd. range here at the house with a steel 36" target scaled to duplicate a 600 yd. X-Course High Power target. My first attempt at it, fired prone with only a sling for steadying the rifle, with said rifle turned out pretty darned good I thought. Four of the shots are actually in the 10-ring with one in the X:
Really, I found it very difficult to improve on the accuracy of GP-11. Considering the fact that it's only 55¢ or so per round, it's hardly worth reloading for the cartridge if you're just wanting match ammo.
35W
