Device for quickly replacing a magazine

A device for quickly replacing the magazine of a handheld automatic small arm having a bullpup configuration relates to military equipment and is intended to maximally reduce the time for replacing a spent magazine and to increase the amount of ammunition that can be carried. Once a Magazine is spent, the bolt comes to rest on a bolt stop. In an embodiment involving a bolt stop the shooter removes the active magazine using a control key. Upon return the control key releases a pivoting tray that is held by a latch spring and the pivoting tray moves into a bottom position. The shooter takes hold of the part of a spare magazine which protrudes from the butt and moves the spare magazine into a magazine opening. The bolt stop releases the bolt, which under the effect of a bolt spring advances grips a round from the active magazine and rams it into the chamber. Firing can be continued immediately.