Operation And Function

This chapter includes the cycle of operation; operating precautions; clearing; disassembly and assembly; loading; malfunctions, stoppages, and corrections; operations under adverse conditions; and destruction of the MK 19. Refer to Appendix B, Operations Checklist, for procedures to be used before, during, and after operation of the MK 19 and Appendix C, Stoppages, Malfunctions, Immediate Actions, and Remedial Actions, for procedures to correct stoppages and malfunctions.


The MK 19's cycle of operation includes six steps: charging, extracting (delinking), cocking, firing, blowback, and automatic feeding. More than one step may be done at the same time.

a. Charging. The charger handles are used to pull the bolt (1) to the rear, aligning the round with the bolt extractors. The rearward movement of the bolt causes the primary drive lever (2) to move to the left, which moves the secondary drive lever (3) to the right. The forked end of the secondary drive lever, which rests on the feed slide pin (4), moves the feed slide (5) to the right. The feed pawls (6) on the feed slide move the linked rounds (7) over one place in the ammunition-feed area of the receiver. The leading round (8) lines up with the bolt extractor (9). See Figure 2-1.

Round CartridgeMk19 Feed Pawls
Figure 2-1. Charging cycle.

b. Extracting (Delinking). When a round is stripped from the belt, it is extracted or "delinked." This happens, after the MK 19 has been charged once, when the trigger (10) is pressed. The bolt slams forward and the bolt's extractors (11) snap over the rim of the cartridge case. When the MK 19 is charged again, the extractor pulls the leading round to the rear and separates the male and female links. The curved edge of the vertical cam (12) forces the lead round out of the extractors and into the bolt fingers (13). With the bolt completely to the rear, the round lines up with the chamber (14), and is ready to fire. As the original leading round chambers, the next round aligns with the bolt extractors. See Figure 2-2.

Benelli Nova Firing Pin Spring
Figure 2-2. Extracting (delinking) round.

c. Cocking. The rearward movement of the bolt causes the cocking lever (15) to retract the firing pin (16). When the cocking lever hits the rear end of the left receiver rail slot (17), the cocking lever is forced forward. When the cocking lever retracts the firing pin, the firing pin sear holds the firing pin to the rear (18). See Figure 2-3.

Cycle Operations
Figure 2-3. Cocking the MK 19.

d. Firing Cycle. The safety switch is on F (FIRE). Pressing the trigger (20) depresses the tip of the receiver sear (21). The receiver sear disengages the bolt sear (22), which releases the bolt forward under spring pressure with a round in the bolt fingers. The cocking lever hits the forward end of the left receiver rail slot, forcing the lever to the rear. The bolt sear hits a plate in the bottom of the receiver, which pushes the firing pin sear up to release the firing pin. A combination of the bolt's inertia and pressure from the firing pin spring drive the firing pin forward. The tip of the firing pin detonates the primer. The round is not completely inside the chamber at the moment the weapon is fired. The cartridge case, held by the bolt fingers, protrudes from the chamber (23). The explosion forces the projectile down the bore. See Figure 2-4.

Rail Gun 40mm Projectile
Figure 2-4. Firing cycle.

e. Blowback and Automatic Feeding Cycle. The gases from the burning powder force the bolt, with a new round in its extractors, to the rear. During this blowback, several things happen at once. First, the curved rail of the vertical cam delinks and forces down the new round on top of the spent case, which forces the spent case out of the bolt fingers and ejects it out the bottom of the gun. Next, the feed slide assembly pulls the rounds to the right in the receiver ammunition feed area, where a new round is ready to pick up (automatic feed). During the bolt's travel to the rear, the cocking lever is pushed forward, which cocks the firing pin. When the bolt reaches the limit of its rearward travel, the recoil springs (24) are completely compressed. The bolt buffers (25) absorb over-travel, reducing trunnion load (recoil force) at the gun-mount attaching points. The bolt sear will not engage the receiver sear if the trigger is still depressed, and another firing cycle occurs. Release of the trigger causes the bolt sear to engage the receiver sear, which prevents the bolt from going forward, and firing stops. See Figure 2-5.

Figure 2-5. Blowback and automatic feed.


Precautions are taken before, during, and after firing of the MK 19.

a. Before firing the weapon ensure that:

(1) The correct ammunition is on hand.

(2) The ammunition is clean and dent-free.

(3) All ogives on the cartridges are tight.

(4) The line of fire is clear of obstructions.

b. While firing the weapon ensure that:

(1) The top cover is closed.

(2) The muzzle of the MK 19 is pointed downrange at all times. NOTE: In the event of a runaway gun, lower one of the charging handles.

(3) Use the suggested three to five-round bursts.

c. After firing the weapon:

(1) Unload and clear the MK 19.

(2) Note weapon discrepancies and report them to the armorer.

(3) Clean and lubricate the MK 19 before storage.


The MK 19 is cleared differently in a firing situation than in a nonfiring situation.

a. Firing Situation. In a firing situation, use the following procedures to clear the MK

(1) Move the safety switch to S (SAFE) (Figure 2-6).

Mk19 Grenade Launcher Back Plate
Figure 2-6. S (SAFE) position.

(2) Open the top cover assembly (Figure 2-7). If all the ammunition has NOT been fired, the bolt is to the rear and a round is on the bolt face. If the bolt is forward, lock it to the rear.

M79 Bayonet
Figure 2-7. Opening the top cover assembly.

(3) Take the ammunition from the feed tray by reaching beneath the feed tray and pressing the primary and secondary positioning pawls. While pressing the position pawls, slide the linked rounds out of the MK 19 through the feed throat (Figure 2-8).

Feeder Delinker Details


Figure 2-8. Removal of linked rounds from feeder.


Figure 2-8. Removal of linked rounds from feeder.

(4) Insert a section of the cleaning rod or bayonet through either side of the receiver rail. Place it on top of the live round or cartridge case, as close to the bolt face as possible, and push down. This action forces the round out of the MK 19.

(5) Lower and pull both charger handles to the rear (Figure 2-9).

Mark Bolt Face
Figure 2-9. Charger handles.

(6) Inspect the chamber and bolt face to ensure that no live rounds are in the weapon.

(7) Place the safety switch on F (FIRE) (Figure 2-6).

(8) Maintain rearward pressure on the charging handle, press the trigger and ease the bolt forward.

(9) Place the safety switch on S (SAFE).

b. Nonfiring Situation. In a nonfiring situation, use the following procedures to clear the MK 19:

(1) Place the safety switch on S (SAFE) (Figure 2-6).

(2) Open the top cover assembly.

(3) Lower one or both charger handles.

(4) Pull the charger handle slightly to the rear.

(5) Allow sufficient space between the face of the bolt and the chamber to see both.

(6) Check for live ammunition.

(7) Ride the bolt forward.

(8) Return the charger handle to its original upright position. 2-4. DISASSEMBLY AND ASSEMBLY

Only qualified ordnance personnel should disassemble the MK 19 beyond the steps detailed in this paragraph (Figure 2-10 and Table 2-1).

Grenade Launcher Disassembly
Figure 2-10. MK 19 disassembled.




Top Cover


Secondary Drive Lever


Primary Drive Lever


Vertical Cam Assembly


Backplate Pin


Receiver Assembly


Control Grip Assembly




Guide Rods and Springs


Charger Assembly, Left


Sear Assemble


Alignment Guide Assembly




Flash Suppressor


Ogive Plunger Assembly


Round-Positioning Block


Rear Sight Assembly


Charger Assembly, Right


Feed Tray


Feed Slide


Cover Pins

Table 2-1. Names of the MK 19 major components.

Table 2-1. Names of the MK 19 major components.

NOTE: High friction areas — the under side of the primary drive lever (3), the vertical cam assembly (4), the bolt (8), the area where the feed slide (20) and feed slide tray (19) touch have been treated to prolong the life of the MK 19 — should be handled carefully during cleaning and handling.

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