Pistol multi-functional rear rail module

A pistol, comprising:

• a frame having a rear grip, a trigger facility forward of the grip and an upper surface;
• an elongated slide connected to the frame and operable to reciprocate along the upper surface;
• the frame defining a rear recess open at the upper surface;
• a unitary insert having a major lower portion removably received in the rear recess and having a pair of opposed frame rails extending from the major portion above the upper surface, the frame rail adapted to connect with the slide to constrain reciprocation;
• and
• the rear recess having a rear wall with a forward-facing wall surface, and the major lower portion of the unitary insert having a rear surface abutting the forward-facing wall surface.