Heckler&Koch MR762A1 - Manual (Page 5)

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NOTE: Both the pivot pin and the rear takedown pin are special precision “target rifle”
pins. For disassembly and reassembly, a center detent in the shaft of the pin must be
engaged under pressure and held to move the pins back and forth. DO NOT FORCE
THE PINS. Forcing the pins could damage the rifle and such damage is not covered
under the HK warranty. Contact HK Customer Service with any questions, TEL: 706-
568-1906, EMAIL: [email protected].
17. Magazine – Holds cartridges ready for feeding and provides a guide for positioning
cartridges for stripping and chambering. The magazine provides reload capabilities for
sustained firing. The HK 10-round polymer magazine and optional 20-round magazine
have a specially shaped follower that will not cant during the feeding process. The spring
is stronger and more reliable than standard magazine springs.
18. Magazine Catch/Magazine Release – Holds the magazine (in place) in the magazine
well and allows the operator to release the magazine and remove it from the firearm. The
magazine catch is activated automatically when the magazine is properly inserted into the
magazine well. The magazine catch is spring loaded and when the button is depressed,
the magazine will drop free from the firearm when this control is activated.
19. Lower Receiver – Contains the fire control system for the firearm. The lower receiver
contains the hammer, trigger, disconnector, sear, magazine well, magazine catch/release,
bolt catch/release, selector/safety lever, buttstock assembly with buffer and recoil spring,
pistol grip and trigger guard. The lower receiver is made from an aluminum forging and
provides a beveled magazine well to ease reloading.
20. Pistol Grip – The pistol grip is made so it can be used by a left or right handed
shooter. It has a trapdoor on the bottom so extra batteries, small tools, or other
accessories may be stored. Other AR-type pistol grips can also be installed.
21. Rear Takedown Pin – When the rear takedown pin is depressed, it allows the upper
receiver to pivot on the front pivot pin. This pin is captive and should not be removed.
Like the pivot pin (front takedown pin), the rear takedown pin has a locking shaft that
needs to be pressed while the pins are depressed and engaged for disassembly and
reassembly.
22. Buttstock Release Lever – The buttstock release lever locks the telescopic buttstock to
the tubular rear buttstock extension. The buttstock is adjustable in length in 5 positions.
23. Rear (Diopter) Sight – proprietary HK sight used on many HK firearms, attaches to the
MIL-STD-1913 top rail of the upper receiver. Other sights also applicable.
24. Front Sight – proprietary HK sight used on many HK firearms, attaches to the MIL-
STD-1913 top rail of the Free Floating Rail System (FFRS). Other sights also applicable.
25. Front (Flip up) Sight – proprietary HK sight attaches to the gas block, folds down when
not in use. Other sights also applicable.
INTERNAL PARTS NOMENCLATURE
Muzzle – The muzzle is the area at the end of the barrel and the last area that the projectile
touches before it exits the bore.
Bore – The part of the barrel that the projectile travels through from the chamber to the
muzzle and contains lands and grooves which make the projectile rotate.
7. Trigger – When activated by the operator, initiates the firing sequence. Located inside
the lower receiver, the trigger when squeezed with the firearm loaded and off “safe” will
fire the gun, “SEMI-AUTOMATIC” will fire one round each time the trigger is pulled. The
MR762A1 uses a proprietary HK two-stage trigger for optimal accuracy.
8. Trigger Guard – The trigger guard protects the trigger. It can be lowered by depressing
the detent with a pointed implement, allowing the use of heavy gloves or mittens to be
used to fire the rifle.
9. Bolt Catch/Bolt Release – The bolt catch/release is manually operated. When the bolt
carrier is pulled fully to the rear, the bottom of the bolt catch/release is pressed by the
operator and then the bolt will be captured. To release the bolt, simply press the top of
the bolt catch/release. The bolt catch/release is also automatically activated when firing
the last round in a magazine.
10. Sliding Buttstock – Attached to the firearm via the receiver extension. The sliding
buttstock is ambidextrous and adjustable to 5 positions for length of pull by pressing in on
the rear portion of the release lever. It also contains the rear sling attachment points. Many
optional buttstocks can be attached to the MR762A1 as long as they fit on the Receiver
Extension (Buffer Tube), which has MIL-SPEC cross sectional dimensions.
11. Forward Assist – Ensures that the bolt is fully closed and locked. The forward assist is
used when a round is not fully chambered. You can push on the forward assist until the
bolt seats the cartridge fully into the chamber. It will return to its rearward position by
spring pressure. It can also be used to silently load the firearm.
12. Case Deflector – Built into the upper receiver, deflects the cartridge cases away from
the operator.
13. Ejection Port Cover Assembly – The ejection port cover is attached to the upper
receiver and is spring loaded. It will open automatically if the charging handle is pulled
to the rear or if the firearm is fired and can be manually closed at any time. It closes over
the ejection port to prevent sand, dust, etc. from entering the chamber. It should remain
closed when the firearm is not being fired.
14. Barrel Assembly – The chamber accepts the cartridge for firing and directs the
projectiles down range. The barrel is cold hammer forged and has standard land and
groove rifling with a 1 in 11 inch (280 mm) twist. The barrel is pressed into the upper
receiver assembly and held in place by the threaded barrel nut.
15. Locking Screws, Free Floating Rail System (FFRS) – The Free Floating Rail System
is fastened with two locking screws to the forward extending barrel locking bushing.
Fastening and positioning of the Free Floating Rail System on the bushing is positive and
ensures maintenance of zeroing on any sight system which has previously been attached
to the rail after removal and remounting of the rail. The Locking Screws are captive and
should not be completely removed, they can be tightened and loosened by using a 5 mm
Allen wrench.
16. Pivot Pin – The pivot pin allows the upper receiver to pivot when the rear takedown pin
is depressed. When both the pivot pin and rear takedown pin are depressed, the upper
and lower receiver groups can be separated. The pivot pin is captive and should not be
removed. Both the pivot pin (front takedown) and rear takedown pin have locking shafts
that need to be pressed while the pins are depressed and engaged.