There is very little technical data available for these weapons so I never quite had enough information in order to do them accurately.
I basically finished up with my M1 and K3 designs and some new data became available that answered a few technical questions I had wrt the design so I decided to take a crack at Gamma-Gerät.
I attached a few pictures showing some initial work in progress and one showing Gamma-Gerät relative size as compared to the Rheinmetall M1 and K3 guns.
I decided to build Gamma in both 1/72nd scale and 1/35th scale and even in 1/72nd scale its a pretty large little model

happy modeling