Values listed in brackets are for alternate (secondary) fire.
The MKb42 is a medium-power assault rifle. It has good damage, a high ammunition capacity, a good magazine capacity, and a reasonably low weight. It serves as a primary weapon capable of dealing with mid-high range enemies as well as crowds of weaker enemies.
Due to the fairly high amount of recoil, it may be useful to switch to semi-automatic (alt-fire) mode to take accurate shots.
Since it has a combination of a good damage, fire rate, and a reasonably high amount of recoil, consider shooting in bursts for maximum accuracy; do not spray and pray if it can be helped.