As the title says, was the MG42 ever used as a coaxial machine gun on German panzers during WW2, or was it only the MG34? Things like the Pz IV, Jagdpanzer 38t, Tiger H, Tiger II, Panther, etc. all used the Mg34 and I'm unsure why the MG42 was never used, at least not to the extent of my knowledge which is why I'm asking here. Thanks
Only one German armored vehicle used the MG42 as a coax gun: the Jagdpanzer IV.
The problem with the MG42 in that role is that it just swallows ammunition, firing at a rate of ~1200rounds/minute. There just isn't room in a tank for that much ammo; tanks are big things, but not that big. The Jadgpanzer IV only carried 1200 rounds for her machineguns.
The Jadgpanzer IV was different, of course. It was designed around the 75mm/Pak 42 cannon and used, in effect, spare parts for everything else. The chassis was that of a Panzer IV, for example. The MG42 was common enough, so they used two (later adjusted to just a single gun).
Otherwise, it was more economical to use slower-firing mgs on tanks.