Abstract: A frame defines a magazine receptacle adapted to receive a removable magazine. The frame defines a first passage receiving a magazine release latch movable between a latched position and a released position. The frame defines a second passage intersecting the first passage and receiving an elongated block element movable between a blocking position in which the block element extends into the first passage to prevent movement of the magazine release latch to the released position, and an unblocked position in which the block element is clear of the first passage to enable movement of the magazine release latch to the released position. The second passage has an opening away from the first passage at a selected surface of the frame abutting a removable upper receiver.

Abstract: A barometric pressure regulator circuit is described. The circuit includes a memory storing output parameters to be supplied to a pressure regulator unit, and a processor operatively coupled to the memory. The processor is configured to perform operations including receiving voltage signals representing output parameters of an engine, storing the received voltage signals in the memory, identifying output parameters to be supplied to the pressure regulator unit that correspond to the received voltage signals, converting the identified output parameters into output electrical signals, and transmitting the output electrical signals to the pressure regulator unit.