You again Wulfe??
You are registered into the McAfee database for sure

1 - Too much dispersion/vibrations: Just go offline, from runaway, max zoom and fire the guns bullet by bullet (shoot-stop-shoot), you'll notice the tremendous dispersion. Dora guns are mounted in the wing roots, not in the middle of the wings, so vibrations should be softer and also dispersion (the guns are more stable). Even more, the, IMO, exagerated vibrations affect much more planes like 190 with a limited frontal field of view than planes like F4U/P51/P47 etc. First shots and you loose the enemy below the sight due vibrations.
Perhaps Tony W. has something to say about the vibrations/recoil effect/dispersion issue of the 151/20 compared to other guns/Mgs.
2 - Low ROF: This is not a whine, this is a fact. ROF may be correct, but add internet effects to it and you'll have very unreliable guns. This is a gameplay issue (or game concession), as 190 hi roll rate was (and was reduced).
Add these two points to the poor trajectory of Mg151/20 bullets and you have the worst weapons in AH inventory.