I’d say that that is more of a drum rather than a revolver. There’s only a single chamber, unlike a revolver where the bullets reside each in its own chamber.

If I’m looking at this correctly, this is a blow back action, the slide pushes the round forward to the chamber out of the integrated drum, and on recoil, the slide comes back, round is ejected, the drum moves a position like a revolver(rather than spring action on a regular drum), and the action moves forward, chambering the next round.