deactivated, the clearing sector arm pivots out of the main cam path. This allows the leaf springs in the rear locking well to force the bolt locking block upward. The bolt roller shaft follows the main cam path that permits the gun to be fired. If necessary, you may clear the gun manually. To do this, manually pivot the clearing sector cam into the main cam path while turning the rotor by hand. For further information on the M61A1 automatic gun, you should refer to the M61A1 Automatic Gun, NAVAIR 11-95M61A1-1. NAVAIR 11-95M61A1-1 provides intermediate-level maintenance procedures and includes associated special support equipment. Q1. Q2. Q3. Q4. Q5. Q6. Q7. REVIEW NUMBER 2 Name the two cycles of the M61A1 gun. When does the firing cycle begin in the M61A1 gun? After the projectile leaves the barrel, what component removes the empty case from the chamber? The main cam path is_______________shaped. List, in sequence, the six operations the breech-bolt assembly performs during a full firing cycle. At what point does the clearing cycle start? The M61A1 gun continues to receive rounds during the clearing cycle. What component ejects all unfired rounds ? AMMUNITION HANDLING AND GUN DRIVE SYSTEMS LEARNING OBJECTIVE: Identify the ammunition handling and gun drive systems of the M61A1 automatic gun. Describe the principles of operation of each system and identify the interrelationship of the various systems. The ammunition and gun drive subsystems are discussed in the following paragraphs. DRUM UNIT ASSEMBLY Live ammunition and expended cases are stowed in the drum unit assembly. This assembly has four major parts-drum unit, entrance cover, exit cover, and scoop disk, Refer to figure 6-12 as you read about these parts. Drum Unit. The drum unit is a cylindrical structure that consists of an outer drum and an inner drum helix, The live ammunition rounds and expended cases are stored radially around the longitudinal axis of the outer drum with their bases in an outward direction. The rounds are suspended by their bases in partitions. These partitions are mounted lengthwise with respect to the inner surface of the outer drum. With the outer drum mounted stationary to the aircraft’s structure, the rounds are moved along the length of the partitions by the rotation of the double-lead helix (inner drum), It’s easy to understand this movement if you think of the inner drum helix as the threads on a screw. The projectile end of the casing protrudes into the threads. As the inner drum helix is rotated, it produces a screwing-type motion, causing the rounds to slide along the partitions from one end to the other end of the outer drum. Entrance Cover. The entrance cover is stationary mounted to the entrance end of the outer drum. The entrance cover contains a retainer gear and 252 steel ball bearings that support the scoop disks and the inner drum helix. The retainer partitions are mounted to the retainer gear that controls the position of the rounds as they are passed from the entrance cover to the scoop disk. A spring-loaded timing pin on the entrance cover is used to index the drum for installation of the entrance unit. Exit Cover. The exit cover is stationary mounted to the exit end of the outer drum. The exit cover is constructed like the entrance cover. It controls the position of the rounds as they pass from the scoop disk to the exit cover. A spring-loaded timing pin on the exit cover is used to index the drum for installation of the exit unit. Scoop Disk. A scoop disk is mounted on each end of the inner drum helix. Each scoop disk has two sets of sprocket spur gears located 180 degrees apart. These spur gears mesh with the retainer gear in the entrance/exit covers that provide rotating support for the inner drum helix. The sprockets attached to the spur gear transfer rounds from the entrance cover retainer partitions to the drum partitions, and from the drum partitions to the retainer partitions in the exit cover. EXIT UNIT The exit unit is attached over an opening in the exit cover and geared to the exit cover retainer gear. The exit unit contains two gear-driven sprocket assemblies. The sprocket assemblies remove live rounds or expended cases from the retainer partitions in the exit cover and place them in the conveyor elements. Before you install 6-10