Push the entire bolt and operating rod assembly into the receiver as far forward as possible. Pull the trigger to allow the sear to drop and the group to slide all the way into the receiver Figure Replacing the Driving Spring Rod Assembly. Insert the driving spring rod assembly into the receiver, sliding it all the way forward against the recess in the rear of the operating rod. Push in and lower the driving spring rod assembly to engage the retaining stud into the hole located on the bottom of the receiver Figure Replacing the Butt stock and Buffer Assembly.
Position the bottom recess grooves of the butt stock onto the top of the receiver recess grooves. Slide the butt stock down until it locks in place on the receiver. Ensure the butt stock is secure. Replacing the Handguard. Line the handguard on the bottom of the gas cylinder and push upwards.
The handguard snaps in place. The gunner must perform a function check to ensure that the MB is correctly assembled. Pulls the cocking handle to the rear, locking the bolt to the rear of the receiver. Pulls the cocking handle to the rear, pulls the trigger, and rides the bolt forward. Maintenance of the MB requires certain actions to be taken before, during, and after firing. Changing the barrel prolongs the life of both barrels. If the MB is contaminated by chemical, biological, or radiological agents, the gunner takes appropriate action to reduce exposure and minimize penetration.
The gunner uses towelettes from the MA1 kit to wipe off the weapon. If these are not available, he washes the weapon with soap and water. The gunner uses towelettes or soap and water as previously described. The gunner wipes the weapon with warm soapy water if it is available. If not, he uses towelettes or rags. For more details, see FM This section discusses the operation of the MB machine gun. This includes loading, unloading, cycle of functioning, adjustment of the sights, and use of both the bipod and tripod.
The MB machine gun is loaded from the closed bolt position. The MB is fired, unloaded, and cleared from the open bolt position. The safety must be placed on "F" before the bolt can be pulled to the rear.
Before belted ammunition can be used, it must be linked with the double link at the open end of the bandoleer. It must be free of dirt and corrosion.
In almost all cases, the MB machine gun can be best used when fired from a tripod; the MB's potential for continuous, accurate fire and control manipulation is maximized. However, in some circumstances, the gunner may use the bipod mount. The gunner makes sure the weapon is cleared. He place the safety on "F. This puts the bolt assembly in the rear position. When the bolt is held to the rear by the sear, he manually returns the cocking handle to the forward position, places the safety on "S.
He lowers the feed tray, places the safety on "F," and pulls the cocking handle to the rear. While maintaining rearward pressure, he pulls the trigger and eases the bolt assembly forward. He places the first round of the belt in the feed tray groove, double link leading, with open side of links face down.
He holds the belt about six rounds from the loading end, while closing the cover assembly. Ensure that the round remains in the feed tray groove, and close the cover assembly Figure The MB is carried loaded with the bolt locked to the rear in all tactical situations where noise discipline is critical to the success of the mission.
Trained gun crews are the only personnel authorized to load the MB and only when command directs the crew to do so. During normal training exercises , the MB is loaded and carried with the bolt in the forward position. The gunner unloads the MB by pulling and locking the bolt to the rear position, if it is not already there. He manually returns the cocking handle to its forward position. He places the safety on "S. He performs the four-point safety check see Section III.
Crew members can recognize and correct stoppages when they know how the weapon functions. The weapon functions automatically as long as ammunition is fed into it and the trigger is held to the rear. Each time a round is fired, the parts of the weapon function in a cycle or sequence. Many of the actions occur at the same time and are separated only for teaching purposes.
The sequence of functioning is known as the "cycle of functioning. The cycle starts when the first round of the belt is placed in the tray groove. Then the trigger is pulled, releasing the sear from the sear notch. When the trigger is pulled to the rear, the rear of the sear lowers and disengages from the sear notch. This allows the bolt and operating rod assembly to be driven forward by the expansion of the driving spring rod assembly.
The cycle stops when the trigger is released and the sear again engages the sear notch on the bolt and operating rod assembly. The actuating roller moves the feed lever side to side, which in turn moves the feed pawls. The forward movement of the bolt forces the outer pawls to the right, fully feeding the round.
The inner pawl rides over the round and settles behind it. The rearward movement forces the inner pawl to the right, fully feeding the round. The action of fully feeding a round pushes the link of a fired round out of the side of the gun. The last link in a belt cannot be pushed out and is cleared during the unloading.
The first round is positioned in line with the chamber and is held in position by the cartridge stop and cartridge guide pawl. On trigger squeeze, the nose of the sear is depressed thus freeing the piston rod extension. The driving spring rod assembly pushes the working parts forward. The feed horn strikes the base of the round. The bolt strips the round from the belt link.
The chambering ramp angles downward and, along with the spring tension of the cartridge guide pawl, forces the round toward the chamber. The cartridge guide pawl also holds back the belt link. When the round is fully seated in the chamber, the extractor snaps over the extractor rim of the cartridge, and the ejector is depressed. During chambering, as soon as the piston begins to move, the firing pin is withdrawn into the bolt block. The breech remains locked during the primary movement.
The bolt enters the barrel breech as the operating rod is driven forward by the drive spring, and as the locking lever, which the bolt is riding on, swings forward, pushing the bolt forward and locking it to the barrel breech. Although the term "locking" is used here, in the MB, the bolt and barrel do not physically interlock.
This way, the barrel can be removed when the bolt is forward. As the working parts come forward and the round is fed into the chamber, the locking lever is forced down by the locking cams. This slows down the forward movement of the bolt assembly. The piston rod extension, still moving forward, causes the locking lever link to rotate downward and back.
This forces the arms down to their fullest extent in front of the locking shoulder. The extractor rises over the base of the round and the ejector is compressed. The round is now fully home with the breech locked. The final forward movement of the piston extension drives the firing pin through the bolt assembly onto the cartridge primer and fires the round. The working parts are now fully forward. When the round is fired, some of the gases pass through the gas plug regulator into the gas cylinder.
The rapidly expanding gases enter the hollow end cap of the gas piston and force the operating assembly to the rear. This powers the last four steps in the cycle of functioning. During the primary movement of the operating rod assembly, it moves independently of the bolt for a short distance. At this point, the locking lever begins to swing toward the rear, carrying the bolt with it into its unlocked position, and clearing the barrel breech.
When the bolt assembly has been jerked back, slightly enough to unlock the breech, the primary effort is extraction of the empty case. When the breech is fully unlocked and the bolt assembly starts its rearward movement, the extractor withdraws the empty case from the chamber. As the cartridge case is withdrawn from the chamber, the ejector pushes from the top, and the extractor pulls from the bottom.
The casing falls down from the face of the bolt as soon as it reaches the cartridge-ejection port. The empty belt links are forced out the link ejection port as the rearward movement of the bolt causes the next round to be positioned in the tray groove. As the working parts continue toward the rear, the return spring is compressed; the trigger is kept squeezed; sufficient is gas made available by the gas-regulator adjustment, which causes the working parts to rebound off the buffer; and the action of feeding and firing continues.
In releasing the trigger, the sear remains down, but the tripping lever rises. As the working parts come to the rear, the end of the piston rod extension hits the tripping lever, which, in turn, allows the sear to rise and engage the sear notch, which holds the working parts to the rear. This paragraph provides information on how to make corrections if the initial setting is not accurate. At a meter target, each paster is 1 cm.
Therefore, ten clicks on the adjusting screw windage of the front sight assembly in either direction moves the strike of the round left or right 1 cm. One complete turn on the front sight blade moves the strike of the round up or down 1 cm.
Elevation Correction. If the shot group is above or below the point of aim, the front sight posts must be adjusted using the front sight-adjusting tool.
Unlock the front-sight retaining strap and rotate it up. If the shot group is above the point of aim, rotate the sight post counterclockwise. If the shot group is below the point of aim, rotate the sight post clockwise. Rotating the front sight post counterclockwise brings the point of impact down on the target. Rotating the front sight post clockwise brings the point of impact up on the target. At a range of 10 meters, one-half turn of the front sight post blade will move the point of impact by 5 mm or.
One full turn of the front sight post blade moves the point of impact by 1 cm. After rotating the front sight post blade the desired amount, lower the retaining strap, but do not lock it down until elevation is confirmed. If the front sight post blade must be rotated counterclockwise to a point where its base is past flush Number 2 blade , it should be replaced with a Number 1 front sight blade, which is smaller than a Number 2 blade. If the front sight post blade must be rotated counterclockwise to a point where its base is more than one full turn past flush Number 1 blade , it should be replaced with a Number 2 front sight blade which is taller than a Number 1 blade Table Windage Correction.
If the shot group is to the left of the point aim, move the front sight assembly to the right to shift the point of impact to the left towards the point of aim. Using the front sight adjusting tool, loosen turn counterclockwise the adjusting screw on the front sight assembly the desired amount. Then tighten turn clockwise the opposite side screw on the left exactly the same number of clicks. At a range of 10 meters, one complete rotation of the adjusting screws will move the point of impact 8 mm or.
As the adjusting screws are turned, noticeable clicks eight per revolution should be detected. Each click is 1 mm or. If this is not the case, have your armorer repair it. The front sight windage adjusting procedure is the combination of creating slack on one side, and then taking up that slack from the opposite side. The front sight protector assembly should always be clamped between the heads of the two opposing screws.
Remember, each time one screw is loosened or backed off, the opposite screw must be turned exactly the same amount. Check for play in the front sight assembly by lightly clamping it between finger and thumb and attempting to move the sight assembly laterally. If you feel no play, the windage adjustment is completed. If evident, carefully check both screws for looseness Table Ten-meter zero mechanical zero is the standardized starting point for all weapons in the United States Army.
The gunner places the range scale on a range of meters on the rear sight. He gets the front sight post blade approximately centered for both elevation and windage. The gunner identifies what number blade is on the weapon for elevation.
Unlock the retaining strap and unscrew counterclockwise until the base of the blade is flush with the front sight protector surface, then make one full turn counterclockwise. This should put the base of the blade past the base of the protector. Screw in clockwise , counting the number of turns it takes until it stops, making sure the blade is on line with the barrel.
If needed, back off until the blade is on line. Unscrew counterclockwise half the number of turns. This brings the blade to about the center. Unlock the retaining strap and unscrew counterclockwise until the base of the blade is flush with the front sight protector surface. Screw in clockwise , counting the number of turns it takes until it stops, making sure the blade is on line with the barrel, if needed back off until the blade is on line.
This procedure brings the blade to about the center. Assume the prone position and sight on the target. Ensure windage is accomplished by making sure the front sight protector is centered left and right on its base. Elevation correction chart. Table Windage correction chart. The MA1 tripod provides a stable mount for the MB, and it permits a higher degree of accuracy and control.
The tripod is recommended for marksmanship training and defensive employment. Mounting the MB on the Tripod.
The tripod assembly provides a stable and relatively lightweight base that is far superior to the bipod. The tripod may be extended and collapsed without difficulty.
It consists of a tripod head, one front leg and two rear legs, and traversing bar. The traversing bar connects the two rear legs. It is hinged on one side, and has a sleeve and sleeve latch on the other that allows the tripod to collapse to a closed position for carrying or storage, or to lock in an open, extended position for use.
The increments are numbered every mils to mils right of center. On the bar, there is a scale that measures direction in mils. It is graduated in 5-mil increments and numbered every mils to mils left of the center. As the traversing handwheel is turned, the muzzle of the weapon turns to the left or right depending on the direction it is turned. Each click of the traversing handwheel indicates a 1-mil change in direction of the muzzle: 1 click equals 1 mil.
There is a total of mils traverse 50 mils right and 50 mils left of center. The elevating handwheel has a mil-click device built into it 1 click equals 1 mil. Engraved into the handwheel is a scale divided into 5-mil divisions and 1-mil subdivisions for a total of mil increments. There are mils above and mils below the zero mark for a total of mils in elevation change. Elevation readings are taken in two parts. First, the major reading is taken from the elevation screw plate.
The second, minor reading is from the handwheel. Direction readings are taken from the scale on the traversing bar, using the left side of the traversing slide as an index. The direction of the reading comes from the position of the muzzle, not the position of the slide. The flex-mount enhances the stability of the tripod platform and dampens the recoil of the weapon. First center the elevating and traversing handwheel. The gunner rotates the traversing handwheel towards his body as far as it will go, then he turns it away two complete revolutions.
He checks the traversing handwheel scale to ensure the "0" on the scale is aligned with the "0" index line before and after the two revolutions. Release the pintle lock 3 on the tripod leg assembly to secure the pintle assemblly to the tripod Figure NOTE : The deflector on the fork assembly should deflect to the right.
Tilt the muzzle down slightly and insert the weapon's front receiver bushing 1 into the slots in the pintle assembly 2. Insert the quick-release pin 3 through the pintle 2 and front receiver bushing 1. Lower the rear of the weapon into the fork assembly 4. Align the mounting holes 5 in the trigger housing with the hole in the fork assembly 4. Insert the spring pin 6 through the holes in the trigger assembly and fork but make sure the weapon is securely attached.
The gunner dismounts the MB from the MA1 tripod by first removing the spring pin from the fork assembly, then he disengages the quick-release pin from the pintle and the front receiver bushing. Now, he raises the weapon up and off the tripod assembly.
The bipod assembly is used to fire from the prone position. The buttstock in conjunction with the gunners nonfiring hand provides support for the weapon when firing in the bipod mode. The gas cylinder holds the bipod in place. To lower the bipod legs, the gunner depresses the bipod retaining latch, while holding the bipod legs together to disengage from slots in the receiver.
Then rotate the bipod legs down and release them so they lock in the vertical position. The bipod legs of the MB do not extend Figure To return the bipod to the locked upright position, the gunner holds the bipod legs together to disengage them from the locked vertical position.
Then he rotates the bipod legs rearward, depressing the bipod retaining latch, and engage the bipod leg hooks into the slots of the receiver. The bipod retaining latch will return to its original position, locking the bipod legs into position. The MA1 tripod provides a stable mount for the MB, and it permits a high degree of accuracy and control.
The gunner unfolds the front leg and positions it toward the target and spreads the rear legs until the leg lock engages. This section identifies some of the problems that cause the weapon to perform improperly. It also explains how to identify unserviceable parts, and how to destroy the MB when authorized to do so.
A malfunction occurs when a mechanical failure causes the weapon to fire improperly. Defective ammunition or improper operation by the gunner is not considered a malfunction. Sluggish operation and uncontrolled fire are the most common malfunction. If cleaning and or lubricating the weapon does not fix the problem, then the gunner turns it in to the unit armorer. Table shows malfunctions, their probable causes, and the corrective actions. Uncontrolled fire runaway gun.
Broken or stuck. Broken of damaged. Uncontrolled Fire Runaway Gun. Uncontrolled fire the weapon continues to fire after the trigger is released. This is usually caused by, the gunner not pulling and holding the trigger all the way to the rear. The following are immediate actions for uncontrolled fire:. Sluggish Operation.
Sluggish operation is due to excessive friction caused by carbon build-up, improper lubrication, or burred parts. Corrective action includes cleaning, lubricating inspecting, and replacing worn parts. The gunner may adjust the gas regulator to maintain the rate of fire until he has a chance to clean the machine gun. A stoppage is any interruption in the cycle of functioning caused by faulty action of the weapon or faulty ammunition.
Stoppages are classified by their relationship to the cycle of functioning. Table shows types of interruptions or stoppages, their probable causes, and the corrective actions. Insufficient gas pressure. Clean gas port, inserts, and gas plug.
Failure to chamber. Ruptured cartridge case. Failure to extract. Broken extractor or spring. Chipped or broken extractor. Defective extractor plunger. Clean and lubricate as required. Failure to lock. Dirty Chamber. Failure to fire. Faulty ammunition. Failure to cock. Broken sear. Broken, defective, or missing sear plunger and or spring. Send to DS maintenance. Short to recoil. Clean gas port and operating rod tube.
Lubricate as required. Replace operating rod spring. See runaway gun Malfunctions. NOTE: When applying immediate or remedial action on a cold or hot gun, the gunner checks to see if any part of the round ranging from the tip of the bullet to the rim is in the chamber. The gunner removes the ammunition from the feed tray only, then closes the cover and attempts to fire. If the weapon fires, he reloads and continues firing. If it does not fire, he clears the weapon, and he inspects the weapon and ammunition.
Immediate action should be taken in the event of either a misfire or a cook off. A misfire is the failure of a chambered round to fire. Such failure can be due to an ammunition defect or faulty firing mechanism. A cook off is the firing of a round by the heat of a hot barrel and not by the firing mechanism. Cookoffs can be avoided by applying immediate action within 10 seconds after a failure to fire.
If the MB stops firing, the gunner performs the following immediate actions are taken. An effective memory aid is POPP, which stands for pull, observe, push, and press. Pulls and locks the cocking handle to the rear while observing the ejection port to see if a cartridge case, belt link, or round is ejected.
Ensures that the bolt remains to the rear to prevent double feeding if a round or cartridge case is not ejected. If a cartridge case, belt link, or a round is ejected, returns cocking handle to forward position, aim on the target, and presses the trigger.
If the weapon still does not fire, takes remedial action. If a cartridge case, belt link, or round is not ejected, takes remedial action. Remedial action is any action taken to determine the cause of a stoppage and to restore the weapon to an operational condition. This action is taken only after immediate action did not remedy the problem. Cold Weapon Procedures.
When a stoppage occurs with a cold weapon and immediate action has failed, the gunner uses the following procedures. Returns the cocking handle and places the safety to SAFE. Reloads and continues to fire. Hot Weapon Procedures. If the stoppage occurs with a hot weapon rounds or more in 2 minutes or as noted above for training , the gunner moves the safety to SAFE, waits 5 seconds during training, lets the weapon cool for 15 minutes , uses the same procedures as outlined for cold weapon procedures.
Jammed Cocking Handle. If a stoppage occurs and the cocking handle cannot be pulled to the rear by hand the bolt may be fully forward and locked or only partially forward , the gunner takes the following steps. Do not try to force the cocking handle to the rear with your foot or a heavy object. This could damage the weapon. Ensures rearward pressure is kept on the cocking handle until the driving spring rod assembly is removed.
Opens the cover and disassembles the gun. The assistant gunner helps the gunner do this. Uses cleaning rod or ruptured cartridge extractor if necessary. If the weapon fails to function properly, the gunner sends it to the unit armorer. Stuck barrel is the result of the machine gun crew not properly cleaning the gas cylinder and gas regulator plug.
During training or range firing the MB should be cleared, disassemble and cleaned immediately. In combat, the MB should be cleaned as soon as possible.
The gun crew performs the following actions, only if the weapon can not be properly cleaned at that time. Pulls the cocking handle to the rear, locking the bolt.
Places the weapon on the ground or away from his face and opens the cover, performs the four-point safety check. The gunner ensures that the barrel is still locked to the receiver with the carrying handle to the right. The assistant gunner places the heat protective mitten on his right hand. With the mitten on he will remove the gas regulator collar from the barrel that is secured to the receiver. With the gas regulator collar removed, the gunner and assistant gunner remove the barrel as outlined in Section II.
After removal of the barrel, the assistant gunner will remove the gas regulator collar and gas regulator plug from the spare barrel. With these removed the gunner and assistant gunner inserts the barrel into the socket of the receiver ensuring that the gas regulator plug is going into the gas hole bushing.
Once the barrel is secured to the receiver the assistant gunner secures the gas regulator collar on the gas regulator plug. The gunner, after ensuring the barrel is secured to the receiver 2 to 7 clicks and the collar is secure, will reload and continue firing. Destruction of any military weapon is only authorized as a last resort to prevent enemy capture or use.
This paragraph discusses the field-expedient means of this destruction; it does not replace published policies. In combat situations, the commander has the authority to destroy weapons, but he must report this destruction through channels.
Disassemble the weapon as completely as time permits. Use the barrel or tripod mount to destroy the bolt and operating rod assembly, barrels, rear and front sights, and mounts. Bury the disassembled weapon or dump the parts into a stream, a sump, or a latrine. Burn the weapon by placing an incendiary grenade on the receiver group over the bolt with the cover resting on the grenade and detonating the grenade. Smash the traversing and elevating mechanism and pintle assembly. Bend the tripod legs.
Subscribe Now! Sign In Sign Out. Site maintained by: John Pike. Pulling the trigger maybe necessary to lower the sear and allow the bolt to release. Some heat distortion or charring may be observed on the outer nonmetallic portion of the heat shield and is not cause for replacement. Always turn both barrels in with the weapon if damage is found on the bolt assembly. CAUTION When inserting the scraper-extractor combination tool into the gas cylinder, ensure before scraping that it is fully seated against the fore-end face of the cylinder.
It must remain dry. Driving spring rod assembly. Receiver inner walls. Cover assembly springs, and feed pawls. Trigger housing inside only. The deflector on the fork assembly should deflect to the right. Broken or stuck Trigger. Broken of damaged sear spring.
O- Lightly lubricate driving spring. The extractor rises over the base of the round and the ejector is compressed. Use at high settings induces added stresses on the action and results in a shorter service life of the weapon. The tripod may be extended and collapsed without difficulty. The various versions of the M have entirely replaced all the M60 versions, though they have for most main applications and roles.
After cleaning, return to Setting 1 for firing of standard ammunition. Trigger Housing Assembly E — Controls the firing of the machine gun. Using cleanina rod and swab item 8. Stoppages are classified by their relationship to the cycle of functioning. Apply slight pressure to the handles 2m40b turn clockwise to remove carbon Figure This is for informational purposes only and is not authority to requisition the listed ym.
Engraved into the handwheel is a scale divided into 5-mil divisions and 1-mil subdivisions for a total of mil increments. Ammunition removed from the airtight containers, particularly in damp climates, may corrode. MN- Designed with front and rear sights, and configured for mounting on water craft. Archived from the original on Inspect the tripping lever and sear for burrs on edges. The MD is issued for aircraft configuration.
Release charger cable or return cocking handle assembly to fully forward and locked position. Direction readings are taken from the scale on the traversing bar, using the left side of the traversing slide as an index. Check that the cocking handle operates the slide properly.
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