I figured it out with this experiment because I have german records from the war with ballistics for the MG151/20 and MK108/30.
Aircraft
109G-2 MG151/20 - 720-250m/s
109-K4 MK108/30 - 500m/s
Testing Procedure.
Round 1 at 150 yard convergence.
Round 2 at 650 yard convergence.
Target distances in yards.
50,100,150,200,250,300,350,400,450,500,550,600,650,700,750,800,850,900,950,100
Take off with each aricraft auto level facing north and pull up target.
1. Record number of mil above or below the graticule center at each test distance.
2. Fire the main cannon and record number of mil obove or below target center it patterns at.
150 yard convergence test for gunsight center.
109K4 - (0.0mil at 50) to (-14mil at 750)
109G2 - (+3mil at 50) to (-14mil at 900)
650 yard convergence test for gunsight center.
109K4 - (-2mil at 50) to (-15 at 750)
109G2 - (+2mil at 50) to (-14 at 900)
Shooting Test at 150 yards.
109K4 - (+7mil at 50) - (-44mil at 750)
109G2 - (-5mil at 50) - (-37mil at 900)
Shooting Test at 650 yards.
109K4 - (+2mil at 50) - (-35mil at 750)
109G2 - (-4mil at 50) - (-31mil at 900)
Results of Testing.
MK108 convergence 150: +.01 angle at 500m/s.
Mk108 convergence 650: 0.00 angle at 500m/s.
MG151/20 convengence 150: +.01 angle at 720-750m/s
MG151/20 Convergence 650: 0.00 angle at 720-750m/s
I tested a number of other aircraft. Lower guns angle up to meet hood mounted MG. Wing guns shoot almost straight out with the line of the aircraft unless there are hood guns. They pattern up to the level line of the hood guns from 150 out to 650 at which point they both converge at the center of the gunsight. HUB nounted cannons are at level with the engine when pulled to full 650 convergence.
The reason at 650 convergence all of your guns look like they are hitting center of the gunsight is your line of view has been auto tilted down by 5-15mil.
At this point realism would dictate locking the HUB mounted cannons at 650 yards in the aircraft in question.
AI am really dumber than a DumbTruck. Just call me Tonka Boy....