I also never heard about such installations by default tachanka has only MG
German has two standard models German army used lf.3 and lf.5 tachankas armed with 2 Anti-Aircraft machine guns each. Their propose was a little bit different they were mainly use for AA protection with ability to ground fire in polish a soviet army they were mobile MG with AA fire as an option

MG Wagen 36 (If. 5), German anti-aircraft variant, armed with a double MG34, in Sudetenland, 1938
