An accessory mounting interface and method are disclosed. The interface has an upper portion having a firearm accessory and at least one through hole extending from a first surface to a second surface of the upper portion, the upper portion having a first post portion with a first side surface and a first flange. A first elongated fastener is arranged through the through hole and has a first end extending below the second surface of the upper portion. The interface also has a second post portion that is movable between a first configuration defining a first transverse distance between the first and second side surfaces and a second configuration defining a second transverse distance between the first and second side surfaces, the first transverse distance greater than the second transverse distance. The first flange substantially opposes the second flange when the second post portion is in the first configuration.