Hello,
in one book I have seen that on Jagdpanzer IV from SS-Panzerjäger-Abteilung 12 mounted "Luftwaffen-Doppel-Maschinengewehr", on the right of driver's hatch. The Author of this relation - SS-Hauptsturmführer Karl H. Brockschmidt said that they were "short, easy to rotate and with powerful firepower". Does anyone know what it was and how it looked in practice? Maybe there are some photos?