That would be my guess too. Looks like he is shooting a double-barrel shotgun with black powder shells. Could even be a legal gun, as cowboy action shooting is a thing in germany, afaik.I'd like to point out the HUUUGE smoke cloud every time he fires. It looks like black powder was used instead of smokeless. It was most likely hand made loads, which are impossible to regulate.
This is what black powder looks like when it fires.
The vast amounts of firearms and explosives smuggled into europe hidden under burkas, by the entirely uncontrolled streams of millions of north-african and syrian refugees starting from 2015 are a bigger problem, tbh.there are also secret weapons depots from the cold war all over germany.
and thousand of automatic guns went missing with the collapse of eastern germany.