Manual / Guide · 1989

Armorers Manual for Maintenance and Repair of Rifle 4,92 mm, ACR — TD 2237, First Draft (Heckler & Koch, 1989)

H&K's first-draft armorer's manual (March 1989) for the 4.92 mm G11 ACR rifle submitted to the US test: technical description, principle of operation including the counter-recoil mechanism, maintenance and repair. The Hyper-Burst Mechanisms dive takes the G11's high-rate burst mechanism from it and reproduces its Figs. 2 and 17–19.

Author: Heckler & Koch GmbH
Year: 1989
Type: Manual / Guide
Credit: Heckler & Koch GmbH, Oberndorf, 1989. Copy from the Internet Archive item "G11 Manual and references" (1557677285551-2).

g11
acr
heckler & koch
armorer's manual
counter recoil mechanism
caseless
4.92 mm

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TM: HTD ‘ 2237 | Ist DRAFT _ARIMORERS MANUAL FOR MAINTENANCE AND ~ REPAIR OF © Soe -HECKLER& KOCH = “MARCH 1989 ~ Digitized BhW GS ery OF 7 u & fa er, 4 LL. /AiiVi ea ARMORERS MANUAL FOR MAINTENANCE AND REPAIR OF RIFLE 4,92 MM, ACR TABLE OF CONTENTS PAGE(S) SUBJECT Lis 2 Oo GENERAL INFORMATION 3 = 5 Oo NOMENCLATURE -~6i= 78 Oo OPERATION - TECHNICAL DESCRIPTION 19 - 36 oO PRINCIPLE OF OPERATION 37 - 39 o SPECIAL TOOLING AND SUPPORT EQUIPMENT 40 - 73 o ARMORERS REASSEMBLY AND DISASSEMBLY 74 - 75 oO ARMORERS CLEANING 76 = V7 © ARMORERS GAUGING AND INSPECTION 78 - 81 © ARMORERS TROUBLE SHOOTING 82 - 107 Oo PART REFERENCE NUMBERS AND SCHEMATIC DRAWINGS £O8. ~ "L039 o NOTES HOW TO USE THIS MANUAL This manual provides information on how to perform armo- rers maintenance on the HK-ACR rifle. Only properly trai- ned and authorized personnel should attemp the detailed disassembly, inspection and repair procedures outlined in this manual. Depot level maintenance, such as barrel replacement, is not covered within this manual. Any such procedure or ope- ration not dedicted on described within this manual should be ,considered depot level maintenance. Only the manufactu- rer is authorized at this time to perform any and all de- pot level maintenance procedures. Throughout this manual, it will be necessary to describe and view parts and assemblies from six (6) different views (positions). Each view considers the position of the given item (i.e. part, assembly, group on entire weapon) in re- lations to the imagined position of the operation, refer- _red to as “the operations vantage point”. . ‘This manual must be used in convinction with the operators manual entitled “rifle, 4.92 mm, ACR", HK TD 2236, March 1989 produced by Heckler & Koch. The armorer must first review and understand all of the operator responsibilities as described within the operators manual before attempting to perform any task described within this armorers manual. NOMENCLATURE OPERATING FEATURES RIFLE PARTS AND WHERE THEY ARE RANGE MARKINGS ELEVATION KNOB RUBBER CAP, \ CARRYING HANDLE RUBBER EYEPIECE—» MAGAZINE RELEASE BUTTON : a MAGAZINE PRESSURE VALVE COMBAT CARRYING SLING EJECTION PORT W/COVER HANDGUARD LOCKING TAB (RIGHT) FLOOR PLATE LOCKING RING PISTOL GRIP FLOOR PLATE RIGHT SIDE VIEW NOMENCLATURE OPERATING FEATURES C CONT ) RIFLE PARTS AND WHERE THEY ARE ELEVATION ADJUSTMENT 7 WINDADGE ADJUSTMENT. AMMUNITION INDICATOR RING BUTTSTOCK AMMUNITION LOCKING TAB (TOP) VIEWING WINDOW—_Avizz ine HANDGUARD LOCKING TAB (LEFT) SAFETY /SELECTOR SWITCH OPEN EJECTION PORT INDICATOR MARKS COCKING HANDLE BUTTSTOCK LOCKING TAB (BOTTOM ) SEMI-AUTO St FULLY AUTO THREE-ROUND BURST LEFT SIDE VIEW Optical sight NOMENCLATURE C CONT ) S MATOR ASSEMBLY GROUPS y Barrel & breech assembl 2000 OPERATION TECHNICAL DESCRIPTION GENERAL . The HK-ACR rifle is a_ light-weight, shoulder-fired, select- fire, gas-operated weapon with a rotating breech cylinder that is fed by a fifty (50) round box-type magazine, the am- muntion utilized with the rifle is of a unique caseless de- sign. The barrel, breech mechanism with counterrecoil system and much of the magazine are surrounded by an outer housing constructed from tough impact resistant material. Reliable operation of the rifle is enhanced as critical parts of the weapon are protected from mud, sand and water as well as da- mage due to impact. The overall styling of the HK-ACR ensures easy operation and handling in all positions and modes of fire. All operating controls can be operated by both right and left handed operators. Q’ {oom CENTER PART The center part contains the following features: o carrying handle with integral optical sight o center guide o trigger mechanism CENTER PART WITH OPTICAL SIGHT The center part, carrying handle, and pistol grip are all one piece. The optical sight is integrated in the carrying handle and is protected by front and rear rubber caps. The rear rub- ber eyepiece assures proper eye relief, eliminates glare on the rear lense and protects the operators eye during recoil. The reticle (crosshair) within the HK-ACR optical sight used for aiming is a more or less conventional intersection of a horizontal and vertical line. A stadia feature within the re- ticle pattern is utilized by the operation for range estima- tion. The sight can be adjusted for builet drop at ranges of 400, 500 and 600 m. OPERATION CCONT >? CENTER PART WITH OPTICAL SIGHT (LEFT VIEW) 1. Rubber cap 9. Grip floor plate Z2. Reticle pattern 10. Control brush 3. Carrying handle/sight housing ll. Safety/selector switch 4. Rubber eyepiece 12. Trigger 5. Locking tabs for buttstock 13. System locking lever 6. Center guide 14. Locking tabs for 7. Center part handguard 8. Pistol grip 15. Control disk wrench The center guide, trigger mechanism and optical sight can all be removed from the center part as complete assemblies. On the rear and the front of the center part are locking tabs for securing the buttstock and handguard to the center part. Inside the center part is the system locking lever (S.L.L.). The §.L.L. holds the breech and barrel assembly in a forward position. When the trigger is pulled, the S.L.L. is moved downward allowing the breech and barrel assembly to recoil rearward. Located above the trigger mechanism is the ambidex- trous safety/selector switch. Between the right and left switch, a safety/selector axle is fixed. This axle provides safe, semi-automatic, three-round burst and fully-automatic modes of fire. “Safe”" and the three firing modes are indica- ted on both sides of the center part by painted letters. Whi- te for "safe” and red for "fire". OPERATION C CONT) A grip floor plate with the attached control brush are con- tained within the pistol grip. The control brush is inserted through the open ejection port and into the chamber to check for the presence of around during the clearing procedure. The grip. floor plate is attached to or removed from the pi- stol grip by rotating the locking ring 90° using slight up- ward pressure. When the breech and barrel assembly (B&BA) are mounted in the center part, the front tip of the buffer rod protrudes through the hole in the front plate. The buffer rod is held in place by the spring-activated B&BA release lever, firmly connecting the B&BA to the center part. CENTER PART, FRONT PLATE (FRONT VIEW) Magazine opening (well) Pressure springs B&BA rélease lever Hole for buffer rod ROWONF OPERATION C CONT >) Tne magazine opening supports the magazine within the center part. On the inside of the magazine opening is a rubber gas- ket, that prevents dirt and sand from entering the center part with the magazine in place. The four pressure springs exert pressure against the handguard and the locking tabs which secure it in place. In addition, these four pressure springs assist in desengaging the locking tabs when removing the handguard. CENTER GUIDE The center guide is held firmly in place within the center part. In turn, the center guide supports and guides the bar- rel and the breech assembly within the center part. As the B&BA recoil during firing, the barrel is supported by the forward cylindrical portion (bushing) of the center guide and thé--breech assembly is supported by the guide grooves that run paralell to and above the barrel in the center guide. The magazine opening cover closes automatically when the ma- gazine is removed. When inserting the magazine, the cover is pushed down into the center guide and out of the way. CENTER GUIDE (LEFT VIEW) 1. Magazine opening (well) cover 4. Guide grooves 2. Elbow spring 5. Barrel bushing 3. Center guide OPERATION C CONT ) TRIGGER MECHANISM The trigger mechanism includes the housing and the internal operating parts. The trigger mechanism is fixed into the cen- ter part by the mounting tabs and the locking tab. The trig- ger mechanism is positioned in such a manner that the safety axle passes through the mechanism to interact with the inter- nal parts. When the safety/selector switch is rotated from "safe .to one of the three firing modes, the trigger mecha- nism is free to operate. The gasket around the trigger seals the trigger mechanism to the center part. TRIGGER MECHANISM (LEFT VIEW) Mounting tab Internal parts Housing Mounting handle Locking tab Trigger gasket Trigger kWNE OorANAN The handguard is attached to the center part below the bar- rel. It is secured to the center part by the two locking tabs that engage in the windows located in the handguard. A cylin- drical metal heatsnield is incorporated into the front of the handguard and shields the handguard and the operations hand from heat radiating from the barrel during firing. Sling at- tachment points are located on both sides of the handguard so that the carrying sling can be mounted on both sides of the weapon for right and left hand use. The guide groove aligns the magazine with the center part. - 10 - Opening for safety axle OPERATION C CONT >) 3 HAND GUARD (LEFT VIEW) 1. Guide groove for magazine 4. Sling attachment point 2. Locking tab window 5. Heat shield BUTTSTOCK The buttstock is pushed forward to mount it on the center part. Two locking tabs engage with locking tab windows to hold the buttstock securly in place on the center part. The gasket positioned within the buttstock seals the joint of the buttstock and the center part when they are assembled. By pressing down on the magazine release button, the magazine catch located on the B&BA is actuated. This action disengages the magazine from the B&BA so that it may be withdrawn from the weapon. The magazine release button is sealed to the buttstock by a rubber cap. At the rear end of the buttstock there are sling attachment points on both left and right si- des. - ll - OPERATION CCONT ) The cocking handle is located on the left side of the butt- stock. It consists the following parts: cover cocking handle toothed wheels ejection port ooo0$°0 The cocking mechanism is required to: chamber a round cock the firing mechanism o to unload an already chambered round from the chamber oo The cocking handle has’ to be unfolded away from the body of ‘the buttstock and rotated 360° in a counter clockwise direc- tion (in accordance with the white arrow) until a notilable stop, is felt. Then a short revense (clockwise) rotation of the-icocking handle to "unlock" the handle in advance for the next rotation. The handle is then folded back against the buttstock. The rotations of the cocking handle accomplishes the following actions: o with a loaded magazine is place, a single round will be chambered o the firing mechanism is cocked o without a magazine in place, the last loaded round is ejected from the weapon o the ejection port located on the bottom side of the butt- stock is momentarily opened to allow a chambered round to exit the weapon. ' The high pressure vent on the bottom of the buttstock pre- vents the build-up of high-pressure propellant gas within the tightly-sealed outer housing on which it is fixed. - 12 - OPERATION C CONT ) BUTTSTOCK (LEFT VIEW) 1. Locking tab windows 7. Sealing wheel 2. Gasket 8 Toothed wheel 3. Magazine release button 9. Ejection port 4. Buttstock 10. Cocking handle 5. Sling attachment points 11. Cover 6. High pressure vent 12. Cocking mechanism, cpl. BREECH AND BARREL ASSEMBLY (B&BA) The breech cylinder housing, barrel, counter recoil mecha- nism, and gas system are one complete assembly. The barrel has four lands and grooves with a constant right hand cylin- der. housing and fixed by two solid holding pins. The guide rail is fixed on top of the barrel. The guide rail guides the B&BA along the center guide. The counter recoil mechanism is also attached to the b&ba by a holding pin. A band supports the front of the counter reco- il mechanism to and below the barrel. The groove in the end of the buffer extension engages with the B&BA release lever located in the front of the center part. The control disk is turned by the toothed axle of the actua- tor gear. The control lever is actuated by the camming groove in the control disk. - 13 - OPERATION C CONT >) 17 16 ( i BARREL & BREECH ASSEMBLY (LEFT SIDE VIEW) l. Barrel 10. Breech cylinder 2. Guide rail 11. Clamping plate 3. Breech cylinder housing 12. Stop lever 4. Cylinder stop lever 13. Control lever 5. Catch 14. Actuator axle 6. Ejector 15. Control disk 7. Magazine catch 16. Counter recoil 8. Guide housing mechanism 9. Ejector lever 17. Buffer extension CONTROL DISK If a magazine is inserted, the function of the control lever does not occur. If there is no magazine in place, the control lever actuates the ejector lever during manual cocking. The ejector lever in turn pushes the ejector into the chamber to eject an already chambered round. If a round is not present in the chamber, the ejector passes ineffectually through the Chamber. In addition, the control disk also operates the cylinder stop lever. By this action, the chamber is positioned in either the firing (horizontal) or feeding/ejection (vertical) posi- tion. Futhermore, the control disk stops the movement of the chamber as soon as it is in firing position. This is accom- plished by the engagement of the stop lever and the control disk. ERA = OPERATION (CONT) The catch holds the breech cylinder in the breech cylinder housing, the catch must be disengaged and moved clockwise into it’s uniocked position (approximatly at 11 o’clock). With this movement the rear portion of the catch presses down on the clamping plate and the firing pin is locked in a cok- ked position. The magazine catch engages with the notch on the magazine housing when it is fully inserted into the weapon. The breech cylinder is supported on the right side where the axle of the breech cylinder passes through the supporting arm of the breech cylinder housing. The connecting rod connects the gas system with the actuator gear. The gas system propels the connecting rod back and forth. This movement is converted into a circular motion due to the connection of the connecting rod and the circular ac- tuator gear (similar to the arrangement on the drive wheel of a.~$team locomotive). The circular motion is transferred by teeth to the neighboring spur gear which is connected to the feeding lever. The feeding lever is propelled upwards through the feeding groove. During this upward movement, the angle of the feeding groove moves the top of feeding lever over the top of the first round in the magazine. At the apex of the feeding levers climb, it automatically moves downward to push the cartridge from the magazine into the chamber. = the slide prevents the round being fed into the chamber from a. Passing all the way through the chamber. The slide allows for s Precise positioning of the chambered round within the cham- eeber. The slide is pushed rearward by the lower sealing wheel Pein the buttstock when the cocking handle is rotated which = allows the chambered round to be pushed through the open = ©Jjection port. OPERATION C CONT >) 1910876 BREECH AND BARREL ASSEMBLY (RIGHT SIDE VIEW) 1. Feeding groove 8. Spur gear 2. \~Breech cylinder 9. Actuating lever 3. Support for breech 10. Slide cylinder axle 11. Disconnector 4. Gas cylinder 12. Clamping plate 5. Connecting rod 13. Feeding lever 6. Actuating gear 14. Breech cylinder axle 7. Sear The camming surface located on the underside of the spur gear activates the actuating lever which in turn pushes downward on the clamping plate. The downward movement of the clamping plate compresses the compression spring and at the same time places the firing pin in a cocked position. The disconnector keeps the clamping plate in a cocked positi- on. The disconnector is moved downward by the sear which re- leases the clamping plate. With the release of the clamping plate, the striker rotates the firing pin to strike the pri- mer. BREECH AND BARREL ASSEMBLY (VIEW FROM THE REAR) Striker Axle Clamping plate Firing pin ar wWndeH Compression spring OPERATION CCONT >) MAGAZINE The single-row magazine is inserted into the HK-ACR above the barrel and paralell to it. It’s capacity is fifty (50) rounds. To remove it from the weapon, it must be withdrawn in the direction of the muzzle (forward) after the magazine re- lease button is depressed. Near the open end of the magazine, there is a white ammuniti- on symbol visible. This symbol indicates the proper position for loading rounds into the magazine. On the top side of the magazine there is a white reference line that runs paralell with the barrel. This line indicates the top of the magazine to facilitate correct loading and can be used as an aiming aid when firing the weapon from the hip. A circular transparent ammunition indicator window is posi- tioned on the left side of the magazine near the front. This window allows the operator to see the position of a single red coil of the magazine spring. The position of this red “line” indicates the approximate number of rounds present in the magazine. MAGAZINE (LEFT SIDE VIEW) 1. Indicator line 6. Stop bar tab window 2. Housing 7. Follower 3. Plastic spring 8. Follower spring 4. Magazine catch notch 9. Stop bar 5. Ammunition symbol 10. Ammunition indicator (not visible) window ll. Stop bar tab OPERATION cCCONT) In the magazine housing there are the following parts: o follower spring o follower o stop bar oO plastic spring The follower is connected to the follower spring. This spring pushes the rounds into feeding position. The stop bar is precisely positioned within the magazine hou- sing by the engagement of the stop bar tab within the stop bar window. A spring actuated lever located within the follo- wer engages with serations on the stop bar to prevent move- ment of the follower in the opposite direction of feeding. This action ensures that all subsequent rounds are always in a proper feeding position at the mouth of the magazine. ce tae CARTRIDGE The cartridge (round) is caseless. That means that the pro- pellant is pressed together into a four-cornered (retangular) propellant body. No metallic materials are required to con- tain the propellant (powder) as in conventional cased ammuni- tion. The projectile (bullet) ist completely surrounded by the propellant body and is protected by a plastic cap. For ignition, an impact sensetive primer positioned in the bottom of the propellant body ignites a booster positioned below the projectile. ~! a — 1 set] —— 2 oe CARTRIDGE ae ; spor 1. Plastic cap f 2. Projectile 9 3. Propellant body 4 Lee 4. Booster ; bts 4 5. Primer SEN 1. I ee es The firing pin strikes the primer to begin the ignition se- quence. The primer in turn ignites the booster which ignites the propellant. The bullet is pushed through the plastic cap into and through the barrel. The plastic cap exits the barrel behind the bullet. - 18 - PRINCIPLE OF OPERATION CCONT >?) = og’ <= R Figure #2 e) Wate ) cS ROTATING BREECH BREECH CYLINDER AND CYLINDER AND CHAMBER CHAMBER ROTATING BACK IN FIRING POSITION INTO THE FEEDING POSITION After the round is fired, the breech cylinder is turned by the feeding and firing mechanism counter clockwise into fee- ding position. The next round is chambered and the breech cy- linder is moved back into firing position. TRIGGER MECHANISM When the trigger is pulled, the lower extension of the system locking latch is pushed rearward by the roller. At the same time, the front extension of the system locking latch makes contact with and pushes down on the system locking lever. Now the breech and barrel assembly (B&BA) is free to recoil rear- ward. Simultaneously, the latch is moved forward by the sy- stem locking latch and allows the spring actuated drop safety to move forward and disengage from the sear. ¢ N OO T ECE: THE SEAR CAN NOT MOVE UNTIL THE DROP SAFETY BREAKS CONTACT WITH IT. THIS PREVENTS THE WEAPON FROM FIRING UNLESS THE TRIGGER IS PULLED. - 20 - PRINCIPLE OF OPERATION C CONT 9) Figure #3 TRIGGER MECHNISM. SAFETY AXLE IN SINGLE-FIRE POSITION 1. Breech barrel assembly 5. Sear Z2. System locking latch * 6. Roller 3. . Latch 7. Trigger 4. Drop safety 8. System locking lever The release lever is pushed rearward by the roller when the trigger is pulled. Through this action, the release latch mo- ves'upwards and pushes the front of the sear up which relea- ses the cocked firing pin. The firing pin, in turn, fires the chambered round. - 21 - PRINCIPLE OF OPERATION C CONT >) Figure #4 TRIGGER MECHANISM. SAFETY AXLE IN SINGLE-FIRE POSITION. TRIGGER PULLED \ 1. Release latch . 4. Support lever 2. Sear 5. Release lever 3. Safety axle 6. Roller SINGLE-FIRE In single-fire, the safety axle prevents the support lever from moving. The B&BA is held in forward position by the counter recoil mechanism. If the trigger is released, the B&BA is fixed by the system locking lever and the trigger is moved forward into rest position. PRINCIPLE OF OPERATION C CONT ) THREE+ROUND BURST When firing a three-round burst, the control slide is moved to the left by a camming surface of the safety axle. In this position the support lever can no longer block the movement of the release latch. When the trigger is pulled, the catch is now pushed upwards by the release latch instead of the sear (as occured in sin- gle-fire). The movement of the catch activated the three- round counting mechanism. The first round of the burst is fi- red as in single-fire but the remaining rounds of the burst are automatically fired by command from the three-round coun- ting mechanism. The burst is automatically stopped after the third round is fired. After the last round of the burst is fired, the B&BA moves forward over the release latch and into it’s most forward position. } Figure #5 TRIGGER MECHANISM. SAFETY AXLE IN THREE-ROUND BURST POSITION, TRIGGER PULLED l. Release latch 4. Safety axle 2. Catch 5. Support lever 3. Control‘slide PRINCIPLE OF OPERATION € CONT ) SUSTAINED-FIRE While on sustained-fire, the support lever is pushed rearward by the trigger and holds’ the release latch in a fixed (sta- tionary) position. After .a round is fired and as the B&BA mo- ves forward, the sear makes contact with the fixed immobile release latch. This contact drives the sear upwards which will atuomatically release the firing pin to fire the next round. This sequence is repeated as long as the trigger is depressed and the magazine has rounds in it. Figure #6 TRIGGER MECHANISM. SAFETY AXLE IN SUSTAINED FIRE POSITION, TRIGGER PULLED - 24 - PRINCI PLE OF OPERAT ION C CONT ) TRIGGER/FIRING PIN SYSTEM (LOCK-WORK) When the trigger is pulled, the latch moves forward and all- ows the pressure spring to push the drop safety forward and out of engagement with the sear. The release latch pushes the front of the sear upwards which in turn pulls the disconnec- tor. The firing pin is rotated by the stored energy in the compression spring and ignites the chambered round. ’ a “ = 4 Figure #7 | ere TRIGGER/FIRING PIN SYSTEM. CLAMPING PLATE AND FIRING PIN COCKED. 1. Drop safety 5. Disconnector 2. Latch 6. Clamping plate 3. Release latch 7. Compression spring 4. Sear After firing, the rotation of the breech cylinder recocks the clamping plate by pushing the clamping plate rearward until the disconnector can engage the clamping plate. The compres- sion spring is now compressed again and the sear is in ready position. During sustained fire with the trigger pulled the drop safety remains forward and disengaged from the sear thus allowing the sear to be automatically forced upwards through contact with the release latch as the B&BA moves forward af- ter'firing. Figure #8 TRIGGER/FIRING PIN SYSTEM. CLAMPING PLATE AND FIRING PIN RELEASED 1. Catch 4. Release latch 2. Sear 5. Three-round counting 3. Engagement pin wheel - 25 - PRINCIPLE OF OPERATION C CONT >) To ‘begin a three-round burst, the release latch is moved to the. left by the rotation of the safety axle. In this positi- on, the release latch will push upwards on the catch when the trigger is pulled. The catch in turn pushes upwards on the sear via the engagement pin which is attached to the sear. This action will cause a chamber round to be ingnited by the firing pin. At the same time that the sear releases the fi- ring pin, the rear end of the catch activates the three-round counting meachanism which interrupts the burst automatically after the third round is fired. BREECH CYLINDER DRIVE SYSTEM N OO T ©§©: IN THE STARTING POSITION THE CLAMPING PLATE IS COCKED AND THE SAFETY/SELECTOR SWITCH IS SET ON ONE OF THE THREE “FIRE” PO- -SITIONS. After the round is ignited by release of the firing pin, the projectile gases through the bore. In the forward portion of the barrel a gas port is positioned to vent gas into the gas System from the bore. After’ the projectile has passed this port, gas flows into the gas cylinder and forces the gas pi- ston rearward against the return spring. The connecting rod, which is fixed to the piston, is pushed rearward transferring this rearward movement to the rotating motion of the actuator gear. Figure #9 GAS SYSTEM WITH CONNECTING ROD AND ACTUATING GEAR 1. Return spring 4. Connecting rod 2. Gas cylinder 5. Actuating gear 3. Gas piston - 26 - PRINCIPLE OF OPERATION C CONT ) i HH i Figure #11 | hem BREECH CYLINDER 45° BETWEEN FIRING AND FEEDING POSITION f 1 Breech cylinder 3. Spur gear i 2 Cylinder stop lever 4. Camming bolt A i i d i y H i Pn sieht Sas Figure #12 BREECH CYLINDER IN FEEDING (VERTICAL) POSITION 1. Breech cylinder 4. Camming bolt A 2. Cylinder stop lever 5. Camming groove A 3. Spur gear - 28 - PRINCIPLE OF OPERATION C CONT ) After ‘' the actuating gear has rotated the breech cylinder 90° into feeding position "“Camming bolt A” disengages from "“Cam- ming groove A” located on the breech cylinder. The breech cy- linder is now in feeding (vertical) position and is held in this position by the cylinder stop lever (see figure #12). The round is fed into the chamber after which the control disk (not pictured) causes the cylinder stop lever to disen- gage from the breech cylinder. "“Camming bolt B", located on the actuating gear, enters "“Camming groove B" and turns the breech cylinder counter clockwise 90° into firing (horizon- tal) position (see figure #13 below). Figure #13 BREECH CYLINDER RETURNING TO FIRING POSITION 1. Breech cylinder 3. Actuating gear 2. ‘Cylinder stop 4. Camming groove B ‘lever 5. Camming bolt B FEEDING N OTE: IN THE STARRING POSITION, THE BREECH CYLINDER IS IN FIRING POSITION, CHAMBER HORIZONTAL. The feeding lever is connected to the spur gear. The feeding lever is guided through the feeding groove by a round bolt attached to the feeding lever. - 29 - PRINCIPLE OF OPERATION C CONT ) Figure #14 FEEDING SEQUENCE IN STARTING POSITION, é BREECH CYLINDER IN FIRING POSITION Breech cylinder 4. Feeding groove Spur gear 5. Breech cylinder Feeding lever housing Figure #15 FEEDING LEVER AT APEX OF CLIMB, BREECH CYLINDER IN FEEDING POSITION Breech cylinder 3. Feeding groove Spur gear 4. Feeding lever - 30 - PRINCIPLE OF OPERATION (CONT) The same moment that the spur gear moves the breech cylinder into feeding position, the feeding lever is moved to it’s highest position over top of the first round in the magazine. As the spur gear continues to rotate it draws the feeding le- ver downward through the feeding groove. The feeding lever draws with it a round and pushes it into the waiting chamber. Once the round is completely chambered, the feeding lever is moved backwards and out of contact with the round. At the same time, the cylinder stop lever is desengaged from the breech cylinder thus permitting the breech cylinder to move. The breech cylinder is rotated by the actuating gear 90° co- unter clockwise into firing position. - 31 - ——————— 4-4-pi-ripes + PRINCIPLE OF OPERATION C CONT 9) Figure #16 >» FEEDING LEVER AND BREECH CYLINDER IN FEEDING POSITION Round 3. Actuating gear Breech cylinder 4. Feeding lever Nr COUNTER RECOIL MECHANISM The B&BA is free to move horizontally back and forth in the center part by sliding on the center guide. The counter reco- il mechanism is fixed to the breech cylinder by a pin and to the barrel by the barrel band. The front of the buffer extension is locked into the front plate of the center part and the rear of the extension is fi- xed within the body of the buffer (see figure #17). When a round is fired, the B&BA is pushed rearward by the re- coil impulse. This movement draws rearward the counter recoil mechanism though the buffer remains stationary and fixed to the front plate of the center part. Due to this rearward mo- vement of the B&BA, the buffer spring is compressed within the buffer housing. - 32 - ak WNE PRINCIPLE OF OPERATION aa TUE tht Tn Re: fe eg teu EOE OT a os ens sack Figure #17 BUFFER AT REST POSITION, B&BA FORWARD I ec ry DUCULLURRU Uh Ubon ee Figure #18 € CONT >) BUFFER POSITION DURING SINGLE AND SUSTAINED FIRE Figure #19 BUFFER POSITION AFTER LAST ROUND OF THREE-ROUND BURST COUNTER RECOIL MECHANISM Buffer spring Barrel band Barrel Breech cylinder housing Buffer rFoOoDANOD - 33 - Return buffer Buffer housing Buffer extension Front plate O. Buffer rod PRINCIPLE OF OPERATION C CONT )D The rearward movement of the B&BA during recoil in single and sustained fire is ended after 50 mm (2") of travel. The buf- fer spring dampens the recoil movement and pushes the B&BA forward into it’s rest position (see figures #17 & #18). The buffer rod slows and controls the final forward movement of the B&BA as it comes to rest back into it’s forward position. In three-round burst mode, the B&BA has moved rearward appro- Ximately 110 mm (4 77,5") after the last round is fired. To prevent damage to the counter recoil mechanism, the return buffer acts to dampen the impact of the front of the buffer against the buffer housing (see figure #19). As the return buffer strikes the front of the buffer housing, the braking effect of the hydraulic buffer ceases. FEEDING _The ejector is pushed rearward by the first round in the ma- @azine. When the cocking mechanism is manually operated, a chambered round is ejected from the chamber by the entrance of the first round in the magazine. During this procedure, the control lever is not engaged in the camming slot on the control disk. Figure #20 EJECTOR IN REARWARD POSITION. ROUNDS ARE PRESENT IN THE MAGAZINE. 1. Magazine 4, Control lever 2. Rounds 5. Control disk 3. Ejector 6. Camming slot - 34 - PRINCIPLE OF OPERATION (CONT Dd If the magazine is empty or not in the weapon the ejector guide moves forward under pressure of a compression spring. The ejector is attached to the front portions of the ejector lever and is positioned by the ejector guide over the opening of the chamber (see figure #21 below). Figure #21 EJECTOR IN POSITION TO ENTER THE CHAMBER EJECTION SYSTEM Ejector Ejector lever Ejector guide Compression spring Control lever spring Control lever Control lever bolt Camming slot Control disk &WONEFE ODONDN By :the pressure of the control lever spring, the bolt of the control lever is pushed against the edge of the control disk. If the cocking handle is manually rotated, the control disk is turned counter clockwise and the bolt on the control lever enters the camming slot in the control disk. The upper bolt of the control lever pushes the ejector lever and the ejector downwards. Supported by the ejector guide, the ejector pushes the chambered round down and out of the ejection port (see figure #22). - 35 - PRINCIPLE OF OPERATION C CONT >) Figure #22 ROUND BEING EJECTED 1. Ejector lever 2. Upper control lever bolt 3. Camming slot After ejection of the chambered round is complete, the ejec- tor is pulled upwards and the breech cylinder is rotated 90° into firing position, SPECIAL TOOLING AND SUPPORT EQUIPMENT t The tools:and devices listed below are for use by authorized per- sonnel only for armorers disassembly, reassembly, inspection, re- pair, and cleaning. For normal operators maintenance (cleaning and lubrication) the armorer must also possess the complete clea- ning kit as pictured within the operators manual. The procedure. for the use of the special tooling pictured below is contained elsewhere within this manual. ITEM PHOTOGRAPH USE Control disk Tool used to rotate wrench breech cylinder and chamber when the weapon is disassembled Optical sight Tool for removing and wrench installing the locking ring that retains the optical sight within the carrying handie Hammer , For use in conjunction 100 g with punches for installing and removing roll pins Screwdriver, Used for installing and flat head, m . removing large screws large SS } | Screwdriver, Used for installing and flat head, | removing small screws Small = ae 2.3 x 80 J SPECIAL TOOLING AND SUPPORT EQUIPMENT C CONT )D t ITEM PHOTOGRAPH US Tweezers Tool for positioning and removing small parts and J ED Crakips Triangular Tool for removal of file heavy lead deposits from weapon Ss Drift punch Tool for installing @ 2.4 mm and removing roll @ 1.8 mm pins Reamer For use when removing heavy fouling from gas tube Barrel vice Used to securly hold blocks breech and barrel assembly in vice for maintenance purposes Notched Used to engage and screwdriver a _— ) disengage springs, etc. SPECIAL TOOLING AND SUPPORT EQUIPMENT (CONT) , f ITEM PHOTOGRAPH US Assembly Used for assembly and fixture for disassembly of buffer buffer \ assembly Cleaning kit, For care and HK-ACR maintenance 4.92 mm of the rifle Used to seal and lubricate various parts within weapon Petroleum jelly ¥ ANS i ? et, y * ry Hautschutt i Allawee- uod : GleitmittelD Combination tool Used for assembly, disassembly and cleaning - 39 - ARMORERS REASSEMBLYYDISASSEMBLY GENERAL INFORMATION o Unless otherwise directed, disassembly of parts and major groups is to be carried out in reverse order of reassembly. o These steps are subject to change due to technical modificati- ons to the weapon. o Reassembly is shown by major groups in numerical order. o Read through the entire disassembly or reassembly procedure be- fore attempting it. o After assembling a part or a series of parts, check for the ap- propriate function of that feature. Such as: Free movement of rotation No movement Presence of spring tension Proper positioning of alignment All parts are present All H-clips (holding clips), C-clips (circlips), roll pins, axles, screws and all other fasteners are properly positioned and secured. oo00000 o AS you assemble and disassemble the weapon, always look care- fully at each component for any signs of damage such as: o Excessive wear o Cracks o Burrs, dents, bends o Rust ° Absence of protective finish CAUTION: NEVER INSTALL THE BREECH AND BARREL ASSEMBLY INTO THE CENTER PART WITH THE HANDGUARD IN PLACE. THE B & BA RE- LEASE LEVER MAY NOT PROPERLY ENGAGE WITH THE B & BA IF INSTALLED AFTER THE HANDGUARD IS MOUNTED. - 40 - ARMORERS REASSEMBLY ITEM(S): CENTER PART (1100) TOOLS REQUIRED: o OPTICAL SIGHT WRENCH !ACTION VIEW !REMARKS ! 1 !OPTICAL SIGHT : ! !'1. Install the distance sleeve Optical sight (5000) into the front of the carry- nt ing handle. !2. Find the alignment notch on the body of the optical sight located approximately 1 1/4" from the front lens near the serial number. C) Mounting ring fa Distance sleeve ! ' ! ! ! ! ! ' ! ! { ! ! ! ! '3. Insert the optical sight into ! the rear opening of the ! carrying handle making sure ! ! ! ! ! ! ! 1 ! ! ! ! ! ! ! ! ! ta ° aoe Rubber cap its Rubber eyepiece that the alignment notch is held in about a 2 o’clock position. '4. Push the optical sight completely into the carry- ing handle until - and - o The alignment detent has entered the alignment notch. NOTE: ROTATING THE OPTICAL SIGHT BACK AND FORTH MAY! HELP IN PROPERLY SEATING! THE ALIGNMENT DETENT. ; NOTE: IF THE SIGHT CAN BE TURNED IN THE CARRYING HANDLE THE DETENT HAS NOT PROPERLY ENGAGED AND! THE SIGHT MUST BE RE- POSITIONED. ' ! ! ! ! ! ' ! ! ! ! ! ' ! ! ! ' ! ! ! ! ! ! ! ! t ' I ' ! ! ! ' ! ! ' ' ! ' : : : ! © A loud click is heard ' ! ! ! ! ! ! ! ! ! ! ' ! ! ! ! ! ! ! ! ! ' ! ' ! ' ! ! 1 ! ! ! ! ! ! ' — -— om - 4) - ARMORERS REASSEMBLY ITEM(S): CENTER PART (1100) TOOLS REQUIRED: o OPTICAL SIGHT WRENCH !ACTION VIEW ! REMARKS BLAS i i Front lense . Screw the mounting ring onto the front of the optical sight. NOTE: ENSURE THAT THE WRENCH NOTCHES FACE FORWARD. . Tighten the mounting ring with the sight wrench. CHECK FOR: o NO ROTATION OF THE SIGHT WITHIN THE CARRYING HANDLE - and - oO FREE ROTATION OF THE ELEVATION ADJUSTMENT KNOB. . Replace the front rubber cap and the rear rubber eyepiece. - 42 - mm remem ee ea ee ee me ee ee ee ee ee ee ee ee ee ee ARMORERS REASSEMBLY (CONT) ITEM(S): CENTER PART (1100) TOOLS REQUIRED: !ACTION VIEW ! REMARKS : ! ! !TRIGGER MECHANISM, CPL (3000) ! ! ! ! ' ! ! ! ! ! Mounting tab | Extension Extension STEP 4-6 ! ! ! 1 ! ! ! ! ! ! ! ! ! ' ! ! ' ! J ! 1 ! ! ! ! ! ! ! ! ! J ' ' ’ ! . ! ' * ' ! ! ! ! ! ! ! ' ' ! ' ' ! ! ! ' ! ' 1 ! ' ! ' t ! ' ! ! ! : 1 ! ! ' ! ! ! ! ! ! t 6. . Place the safety/selector switch on "Safe", . Locate the two mounting tabs on the front of the trigger mechanism. These tabs will engage with two mounting notches located inside the center part above the opening for the trigger. . Hold the end of the extension between your index finger and your thumb. . Place the trigger mechanism inside the center so that the trigger protrudes fully into the trigger guard. . Align the two mounting tabs on the trigger mechanism with the mating notches in the center part. Lock the trigger mechanism into the center part by hooking the locking tab on the left side of the exten- sion under the block provided inside the center part. - 43 - ARMORERS REASSEMBLY (CONT) ITEM(S): CENTER PART (1100) TOOLS REQUIRED: !ACTION VIEW ! . ! REMARKS !CENTER GUIDE ! ‘ ! ! + ! 4 ! ‘ ! ' . ! ! . Center guide { * | properly seated ! ! ! ! ’ : ' ' ! ! ! ! ! ! ! ! ! ! ! ' ! ! ! ! ! ! ! ! ! l. Insert the bushing of the : center guide into the ! opening for the barrel in ! the front of the center ! part. : ! ! ! ! ! | ! ! ! ! ! ' ! ! ! ! ! ! ! Keep the magazine well cover pointing up. 2. Engage the rails on the rear of the center guide with the grooves in the center part. 3. Push the center guide fully into the center part until the rear of the center guide is recessed within the housing about 1/4", NOTE: THE CENTER GUIDE IS : HELD IN PLACE WITHIN THE ! CENTER PART BY FRICTION ONLY, BETWEEN THE GROOVES! AS WELL AS BETWEEN THE FOR THE BARREL. t : : ! ! f : ! ! ! ! ! ! ! ' ! ! ! ' ! ! ! ' ! ' ! : ! J ! ! : : t : : ' ! ! BUSHING AND THE OPENING ! ! ! ARMORERS REASSEMBLY ITEM(S): BUTT STOCK (1200) TOOLS REQUIRED: o FLAT HEAD SCREWDRIVER, SMALL o PETROLEUM JELLY © NOTCHED SCREWDRIVER 'ACTION VIEW ! REMARKS ! ' ' !MAGAZINE RELEASE BUTTON : : ! NOTE: BEFORE INSTALLING THE MAGAZINE RELEASE BUTTON OR THE COCKING MECHANISM, APPLY A THIN COATING OF PETROLEUM JELLY BETWEEN THE BUTT STOCK HOUSING AND THE OPERATING PART. WIPE OFF EXCESS AFTER Magazine release button (1201)) ASSEMBLY IS COMPLETED !l. Insert magazine release button into the hole provided on the top of the butt stock. bah C-clip, medium (1200.1) SY '2. Using the notched screw driver, attach a medium sized C-clip to the axle of the button on the inside of the butt stock. ! iJ ! ! ' ! ! ! ! ! ! ' ' ! 1 ! ! ! ' ! J Sealing wheel (1220) |e | H-clip, small (1200.12) Toothed wheel (1200.4) Cocking handle (1200.7) with cover (1200.5) ! ! ! ! ! ! ! ! ! ! ! ! ! ' ! t ! ! ! !COCKING MECHANISM, CPL !