I quite like the gun; it is an iconic WWII weapon, it made me get into armor models (the also iconic DML Flak 88 model), and I built a couple of iterations of it over the years.
And now I found this manual online.
It is great if you made an impulse buy on Ebay, and have no operating manual, but it is also good for reference.
The Butterfingered Modelbuilder's Adventures 