the only way to know for sure what shoots best in your particular rifle, is to try a little of everything.
i did this with my finnish m39's, and kept a log of all results. my testing showed that hungarian lightball was the most consistant, followed by hungarian steelcore hb, and then bulgarian hb. the hung. hb could throw impressive groups, but were not as consistant as the light. (ex. 4 of 5 hits within 1" of eachother, with a flier expanding the group by another 1 to 2+ inches) also hit about 6-7 inches high @ 100 yards. bulgarian for me hits poa @ 100 yards, and pretty much all shots are always on the centerline.
with hungarian lb not readily available at the time, i loaded up on the bulgy.
also tried the russian lb, the czech lb, and a few others. in my rifles they didn't print as well as the the ones above.
store bought commercial top honors go to prvi partisan, followed by wolf bi-metal case. barnaul 203gr sp worked well enough, but brown bear 185fmj's were weak with 3 to 4 inch grouping. found out that all of the "bear" line use .310 bullets, which do not work well in my .311 bores. odd part is brown bear is barnaul -- same people. but the barnaul ammo is made with .311 diameter bullets..
anyway, like i said, try as many different types as you can and record the results before buying in bulk.
for me all this trial and error got me onto the trail of loading my own. just had to see how tiny those groups could get.
they have gotten quite a bit smaller... but i'm still working on it.