There may also be a fundamental issue with flat-trajectory auto weapons shooting at close range targets on open, table-top flat ground. The first round in a burst tends to be at the correct level, but subsequent rounds tend to string higher. Consequently you either get a one bullet hit followed by a bunch of high misses or just a bunch of high misses. Compared to bullets that impact the ground in the area of the target, high misses cause little (or maybe no) suppression. The MG42 ends up have the same effect as a less accurate semi-auto rifle on targets in these circumstances. If the target were in cover with a significant vertical face, however, many more shots would impact in the target area, causing higher suppression.
Trying to figure out a way to test that little hypothesis, but haven't come up with anything yet.