This design was made by a man named William Andrews in the United States in 1918. It’s odd magazine geometry is evocative of a hand held vacuum cleaner (at least to me). The magazine is made up of ten 7rd 1911 magazines in a turret shape. Only one was ever made as it was heavy and by 1918 the war was winding down.
…You’re sure that’s not a prototype Dyson V8?