A machine gun assembly includes, but is not limited to, a receiver, a barrel extension, and an interlock element. The barrel extension is mounted to the receiver and moves between forward and retracted positions with respect to the receiver. The barrel extension is configured for quick-release engagement with a barrel. The interlock element is mounted to the receiver and moves between a blocking position and a clear position. The interlock element has a blocking portion positioned to obstruct movement of the barrel extension to the forward position while in the blocking position and the blocking portion is positioned to permit movement of the barrel extension to the forward position while in the clear position. The interlock element moves to the blocking position when the barrel disengages from the barrel extension and moves to the clear position when the barrel is correctly engaged with the barrel extension.

A toy projectile launcher having a housing, a projectile container, a cocking slide, an air piston assembly, a barrel interface section, and a detachable launch barrel is disclosed. The projectile container is adapted to hold projectiles, such as foam darts. The cocking slide can be moved for-ward and backward. When the cocking slide is moved backward the air piston barrel moves backward, and a projectile is moved in front of the air piston assembly. When the cocking slide is moved forward, the projectile is pushed into the barrel interface section by an air nozzle disposed on the front of the air piston assembly. A first airtight seal is formed between the air piston assembly and the rear of the foam dart, and a second airtight seal is formed between the barrel interface section and the detachable launch barrel.