Interesting video on the FG-42 LMG
Right here. The late Curtis Earl, NFA dealer and expert, told me he thought the design was ripped off from the Johnson Light Machinegun. Externally, they're quite similar, they have similar features (down to the first model FG-42 and the Johnson could have their magazines reloaded from five round clips pushed in the other side of the gun), both are short recoil operated, and both fire from an open bolt in full auto and a closed bolt in semiauto. That's truly a rare combination of features -- it'd be quite a coincidence that two groups working independently designed guns with all of them!
Hat tip to reader David McCleary.l..