I'm translating the 1944 edition of the German Order Police "Weapons and Shooting Technical Guide" book (about 700 pages). This book has information that I've never read anywhere else, and will be available in a few more weeks (I'm proof reading it now).
One matter that has always been questioned, is why the MG42 shoots so fast. Here's what the technical guide has to say about it:
With use as a light MG.
Combat shooting tests have shown that bursts of 5-7 shots produce the best hit results because the shooter is not able to keep the fire on target longer than that.
The destruction of a target is therefore carried out with fire bursts of 5-7 shots, with renewed aiming each time. It is important that the time for setting up is kept as short as possible, so that the fire bursts closely follow each other.
A gunner can use MG. 42 under combat conditions to fire about 22 fire bursts per minute, i.e. around 154 shots.
Comparative shooting under the same conditions with the MG. 34 provided the best results at about 15 bursts of fire per minute of 7-10 shots - so about 150 shots.
Therefore with MG. 42 as a light MG, ammunition consumption is slightly higher than with the MG. 34, but the results with MG. 42 are about 40% better.
So there it is - a faster rate of fire with shorter bursts equals a higher hit ratio for the ammunition shot.