My "hillbilly assault rifle" was previously owned by two other very good cast bullet match shooters. When I got it, at fair price, it still had the birch stock and would shoot match jacketed bullets into about 4 inches and cast into about 6 inches. This was about 2009. I did every modification suggested on the 'net and nothing helped in five years of trying.
Then a guy wanted to sell me the present black stock set very reasonably, and so I put it on and groups went to 2 inches for jacketed and 3 inches for cast. There was something very wrong with the butt stock attachment interface, I finally figured out. Now it is a very reliable inch and a half grouper with Hornady 130 HP's and almost as well with the Lyman 311403 (the Pope bullet).
Who ever made the barrels used .300/.308" spec's but the chamber was cut for using ChiCom 7.62x39. I have heard they quit making these because the Norinco steel bullet MilSup were so over pressure that were wreaking the actions. So it takes some fiddling to make it work well, but it can be done.