Well, the tests seem to imply that the T-34s hull and coaxial MGs are better than the PIV's, though it doesn't support the assertion that they differ in the "Focus Fire" property". Perhaps that isnt what you meant, though. (More than just one test would be nice, incidentally)
I have heard before that the T34/76 and t34/85 do have abnormally strong hull/coaxial machine guns, though knowing the exact statistics would be nice. I'm not certain, but haven't the T34s MGs been tweaked in a patch in the last half-year?
I was making a new video, but my tool doesn't work. ;((
Best you try it your own on Test-map.
My results were WITH active maingun. P4 (with and without upgrade) vs T34/76 and KV1 killing Grens, no cover, ~20 range.
P4 ~14sec. +/- 2sec. (3 times tested)
T34 ~14sec. +/- 2sec. (3 times tested)
KV1 ~15sec. +/- 3sec. (3 times tested)
P4 (upgrade) 12sec. +/- 2sec. (3 times tested)
T34's maingun more often misses vs P4, but MG performs better, it even makes damage without animation. KV1's gun sometimes snipes hard, then it fails, wasn't realy able to see how MG works.
P4 with upgrade is best.