 Here you see a 40 millimeter grenade launcher, which has been removed from an M16A1 rifle. By now, you are probably familiar with the controls and operation of the launcher, and have a knowledge of the preventive maintenance checks and services, as prescribed in technical manual 9-1010-221-14. In order for you to understand the probable causes of malfunctions, so you can apply the proper corrective action, we will explain and demonstrate how the launcher functions. We will start the explanation of functioning with the weapon having fired a cartridge and using a cutaway receiver. Depressing the barrel latch unlatches the barrel by moving the latch out of this recess in front of the barrel extension. The latch has a compression spring which causes it to move into the recess. Forward movement of the barrel causes cocking, extraction, and ejection. Cocking and extraction occur in part at the same time. We will explain each of these actions separately. Cocking. Cocking begins as the barrel begins its forward movement on the receiver. This is the cocking lever. It is mounted on a spring pin in the receiver and can rotate on that pin. The upper end of the cocking lever is positioned in the elongated slot of the barrel extension, like this. The fork of the cocking lever straddles the firing pin in front of the firing pin shoulder. When the barrel and barrel extension are moved forward, the top of the cocking lever is moved forward, causing the cocking lever to pivot on its mounting pin. The fork of the cocking lever is then moved rearward, thus moving the firing pin rearward. The firing pin spring is then compressed because it's positioned between the firing pin and the trigger. The firing pin shoulder is then engaged by the lower sear of the trigger. If the trigger is held squeezed, the upper sear will engage the top shoulder of the firing pin. When the trigger is released, the lower sear again engages the firing pin. Cocking is completed when the barrel has moved about three-quarters of an inch forward. But the barrel must be moved four to five inches forward to permit extraction, ejection, and loading of another cartridge. When the barrel moves fully forward, the barrel extension is moved out of the trigger housing. The barrel extension follower, which is spring-loaded, follows the barrel extension and serves to hold the cocking lever down when the barrel extension moves forward and clears the cocking lever. Without a barrel extension follower, the barrel extension would jam against the top of the cocking lever as the barrel is moved rearward. By holding the cocking lever down with the follower when the barrel extension is moved into the receiver, the cocking lever will again enter into the elongated slot of the barrel extension. When the weapon is loaded and the barrel is closed on the breech, the spring-loaded extractor snaps over the rim of the cartridge to hold the cartridge case to the breech. So after firing, when the barrel is moved forward, the cartridge case is held to the breech by the extractor, thus extracting the cartridge case from the barrel. The ejector is a spring-loaded type plunger. A compression-type spring causes the ejector to protrude through the breech face of the receiver prior to loading. When a cartridge is loaded and the barrel is closed, the base of the cartridge pushes the ejector rearward, compressing the ejector spring. During extraction, as the barrel is moved forward and is clear of the cartridge case, the ejector pushes the top of the cartridge base forward. The cartridge case pivots about the extractor and falls from the receiver. The cartridge is manually loaded into the barrel, only after the barrel is moved fully forward and extraction and ejection are completed. After the barrel has been loaded, it is moved rearward briskly to overcome the extractor spring and ejector spring tension and cause the extractor to snap over the rim of the cartridge. Rearward movement of the barrel causes chambering to be completed and locking is performed by the barrel latch entering into a recess in front of the barrel extension on the barrel. Thus, chambering and locking are the functions performed by the rearward movement of the barrel. The safety is moved to the safe position after loading unless immediate firing is intended. The safety functions to block downward movement of the nose of the trigger sear. This prevents the trigger sear from releasing the firing pin. Thus, preventing the weapon being fired. Firing is initiated by squeezing the trigger. An upward pull on the trigger causes it to rotate slightly on the trigger mounting pin in the receiver. As the trigger rotates on the mounting pin, the firing spring is further compressed. This will add force to the firing spring, which was partially compressed during cocking. The trigger sear on the front of the trigger moves downward while the rear of the trigger is pulled upward. The trigger sear will move away from the shoulder of the firing pin, allowing the firing pin to be driven forward by the compressed firing spring. The firing pin will extend through the breach of the receiver to strike and detonate the cartridge primer, thus firing the grenade launcher. We have seen how the launcher functions in detail and you have learned that forward movement of the barrel causes cocking, extraction, and ejection. Loading is performed manually. Rearward movement of the barrel chambers the rounds and the barrel latch serves to lock the barrel to the receiver. The safety functions to block trigger movement and prevent the weapon from firing. The grenade launcher is easy to operate and maintain because it has few moving parts. An understanding of how the launcher functions will enable you to quickly apply corrective action in the event of a malfunction. Know your equipment, operate it properly, perform preventive maintenance services, and your grenade launcher will always be a dependable weapon.