Cute design, but the original DS Gun is too classic (and simple) to need any "improvement."
The backstory that I would give this is that it is an EARLIER version of the gun, PRE-CITY, used by the City Computer as the basis for the current model. It's a logical extension of standard firearms toward the "new technology," which would be refined into one needing fewer resources to mass produce (vital in the resource-starved world which led to the City in the first place).