People has wanted to combine firearms with bladed weapons as soon as feasible, as partially illustrated by this series of videos. But the compromises needed render the combined object less useful than envisioned. So I thought about making the pistol module both detachable and adjustable to the blade geometry. The magazine design was difficult until I abandoned the ability to attach the pistol both parallel or perpendicular to the blade.

EDIT : Reorganized the drawing and added a top view to clarify the position of the various elements of the pistol.