Agreed on bottom left to upper right dispersion, but nothing massive and as you say very manageable. Not sure about 2Z primer delay, to me it doesn't sound likely, considering SMG fixed firing pin and advanced primer ignition would negate any effect, and no noticeable primer delay on any pistols/ other SMGs firing 2Z that I've heard seen or heard about.Not so much "climb" as a tendency to track a group bottom left to top right (@25m), depending upon the ammo. At least in military full-auto practices it usually meant taking a 7 o'clock poa on the white patch, firing a short burst to 1 o'clock and the resetting the poa.
I suppose some types gives a small residual recoil impulse or slight change in the timing of the firing cycle and the way it changes the gun balance. Perhaps good old 2z has a slight primer delay cf. civvie types?
No, nothing like a 7.62x51 rifle on full auto.