The actions required to replace the bolt stud are almost the same as those required to remove it. (See fig. 13-39.) Align the stud hole in the bolt with the clearance hole in the right sideplate. Ensure the shoulder of the stud fits inside the sideplate.

Replace Driving Spring Group

To replace the driving spring group, press up on the bolt latch. Move the bolt all the way forward by pushing on the bolt stud only. Place the end of the driving spring rod in its hole in the back of the bolt. Then push forward on the driving spring group and the buffer tube. Press in and push the head of the rod to the right. Insert the retaining pin in its seat in the right sideplate. (See fig. 13-38.)

Replace Backplate Assembly

To replace the backplate, hold its latch down and the trigger up. Position the backplate guides in their guideways. Hold the latch lock out and slide the backplate down until the latch snaps into place, as shown in figure 13-46. Release the latch lock and tug up on the backplate assembly to ensure it is firmly seated.

Replace Barrel Group

To replace the barrel group, pull the retracting slide handle to the rear. Do so until the lug on the barrel locking spring is visible through the 3/8-inch hole in the right sideplate. (See fig. 13-36,) Again, insert the smallest loop of a .50-caliber link, or suitable spacer, between the trunnion block and barrel extension. Screw the barrel all the way into the barrel extension. Then, and this is important, unscrew the barrel two notches. Remove the link and close the cover group. That completes the general assembly of the .50-caliber BMG.

OPERATING THE .50-CALIBER BMG

The safest and best way to operate the .50-caliber BMG is to follow established procedures. In doing so, you prevent damage to the gun and injury to yourself and others. The basic operating procedures involve the following steps:

1. Loading

2. Half-loading

3. Full-loading

4. Unloading

Semiautomatic Operation

If single-shot firing is desired, the gun must be set for semiautomatic operation. To do so, you must ensure the bolt latch release is in the up position (or not locked down). (The bolt latch release can be seen in view A of fig. 13-37.)

When the bolt latch release is up, the bolt latch assembly is depressed. In this position, the latch assembly can engage notches on top of the bolt when it (the bolt) is to the rear. Thus, when the bolt recoils after around is fired, it remains locked to the rear.

Depressing the bolt latch release raises the latch assembly. The assembly disengages from the notches on top of the bolt. That allows the bolt to be driven forward into the battery.

To fire the .50-caliber BMG when set for semiautomatic, (1) depress the bolt latch release and (2) depress the trigger. These two actions must be done for each round fired.

Automatic Operation

If automatic firing is desired, the gun must be set for automatic operation. To do so, you must ensure the bolt latch release is depressed and locked down. That is done by turning the buffer tube sleeve. The bolt latch release lock is rotated to engage the bolt latch release, locking it down. (See view A of fig. 13-36 again.) When the bolt latch release is locked down, the bolt latch assembly remains in its up position. Thus, when the bolt recoils, it is automatically free to return forward into the battery.

To fire the .50-caliber BMG in automatic, (1) lock the bolt latch release down and (2) depress the trigger. Short bursts are generally recommended, rather than sustained firings.

Loading Operation

The .50-caliber BMG is loaded manually. This involves placing an ammunition belt into the receiver of the gun. Ammunition for the .50-caliber BMG comes prebelted and is shipped in a standard .50-caliber ammunition box.

To load the gun, open and remove the lid on the ammunition box. Then open and raise the cover group on the gun (fig. 13-47). Insert the double-loop end of the ammunition belt into the feedway of the receiver. Ensure the first cartridge is held by the belt-holding pawl. Close the cover group on the gun and make sure it is latched securely.

If two personnel are operating the .50-caliber BMG, the assistant gunner loads the ammunition belt. The gunner performs the next two operations-half-loading and full-loading.