Firearm magazine retention system with positive positioning feature

A firearm magazine retention and release system providing a motion-limiting engagement between a firearm and a magazine. The magazine is provided with a catch opening. The firearm is provided with a magazine catch having a protrusion positioned to engage the catch opening. The protrusion includes one or more sloping surfaces that provide a greater vertical engagement as the protrusion is urged further into the catch opening. The result is that the protrusion engages one or more edges of the catch opening thereby inhibiting vertical travel of the magazine with respect to the firearm.