Heckler And Koch HK USC Carbine 45 ACP Operators Manual

							®
Operators ManualIn a world of compromise, some don’t.
HK USC Carbine
.45 ACP  
						

							USC
Universal Self-loading
Carbine
Operators ManualCAUTION: Read the safety rules before handling the 
USC Carbine!
®
© Heckler & Koch, Inc., 11/99 (revised June 2001)
All rights reserved
HK, Inc., 21480 Pacific Blvd.
Sterling, Virginia 20166-8903 
United States of America
Telephone (703) 450-1900
Specifications and models subject to change without notice.
.45 ACP 
						

							5
TABLE OF CONTENTS
4TABLE OF CONTENTS
Troubleshooting Guide  ......................................................................33
Carrying Sling  ....................................................................................35
Sights ..................................................................................................36
Exploded Diagram and Parts List........................................................38
Specifications ......................................................................................40
Firearms Service Record ....................................................................41 Safety Rules on the Use of the HK USC ..............................................6
General ................................................................................................8
Assembly Groups ................................................................................10
Description of Assembly Groups ........................................................11
Assembly Group 1  Upper Receiver with barrel ..................................11
Assembly Group 2  Bolt Group  ..........................................................12
Assembly Group 3  Lower Receiver with trigger mechanism  ............13
Assembly Group 4  Buttstock with pistol grip ......................................15
Assembly Group 5  Magazine ............................................................15
Accessories ........................................................................................16
Carrying Sling......................................................................................16
Cleaning Kit ........................................................................................16
Mounting Rails for Aiming Devices according to MIL-STD-1913 ........16
Handling and Operation  ....................................................................17
Filling the Magazine  ..........................................................................17
Emptying the Magazine ......................................................................17
Insertion and Removal of the Magazine  ............................................17
Loading the USC ................................................................................18
Forward Assist ....................................................................................19
Storage of the USC ............................................................................20
Disassembly ........................................................................................21
Safety Check ......................................................................................21
Disassembly into Assembly Groups  ..................................................23
Disassembly and Assembly of the Bolt Group ....................................23
Disassembly and Assembly of the Magazine  ....................................24
Reassembly of the USC  ....................................................................25
Function Check ..................................................................................26
Cleaning & Maintenance ....................................................................27
Normal Cleaning   ..............................................................................28
Major Cleaning  ..................................................................................30
Operator Inspection ............................................................................30
Lubrication ..........................................................................................31
Ammunition..........................................................................................32
Stoppages ..........................................................................................32 
						

							7
USC SAFETY RULES
6USC SAFETY RULES
• Before handling and cleaning the carbine check to ensure that:
- The bolt is locked to the rear
- The carbine is unloaded (cartridge chamber empty)
- The barrel is free of obstructions 
- The magazine is empty.
• Keep your finger off the trigger when loading, unloading or
otherwise handling the carbine. Always place the trigger finger
outside of the trigger guard.
• Never use force when handling, disassembling, cleaning and
assembling the carbine.
• Disassemble the carbine only as far as described in this
manual.
• A handstop is provided with each USC to keep the nonfiring
hand or fingers away from the barrel of the carbine. This
handstop should be used at all times and can be mounted on
the USC with or without the mounting rails attached.
• Always wear eye protection when using the carbine.
• Always wear hearing protection when using the carbine.
• Take into account the fact that bystanders are also endangered.
Ensure bystanders are also wearing ear and eye protection.
• Only use ammunition designed to SAAMI specifications that is
factory-loaded, undamaged, and of the correct caliber. The use
of low powered cartridges (including wadcutter and semi-
wadcutters bullets) could lead to functional stoppages
(including bullets stuck in the barrel) and is not recommended.
• Always mind that the muzzle area is free of obstacles during
firing.
• Store the USC and ammunition in separate places.
• Discharging firearms in poorly ventilated areas, cleaning
firearms, or handling ammunition may result in exposure to
lead, a substance known to be associated with birth defects,
reproductive harm, and other serious injury. Have adequate
ventilation at all times. Wash hands thoroughly after exposure.
• Heckler & Koch does not assume liability for events due to
disregarding this manual, improper handling, negligence,
improper treatment, unauthorized exchange of parts, or
manipulations of the carbine.
• Remember, firearms safety begins with you. Read this operators
manual and be familiar with the safe handling of this firearm
before using it. Store all firearms in a safe and secure location.
Keep firearms away from children. Always be a safe shooter.
Keep this manual with the carbine.
Safety Rules on the use of the HK USC carbine.
Clear the firearm! Before handling the carbine, “clear it!” Do so by:
• Make sure fingers are outside of the trigger guard and the
weapon is pointed in a safe direction at all times!
• ON SAFE – Rotate the safety/selector lever to the “Safe”
position. (With the safety/selector lever set at the white box with
a white bullet symbol inside.)
• REMOVE MAGAZINE – Depress the magazine release lever and
remove the magazine from the magazine well.
• COCKING LEVER – Rotate the ejection port towards the ground
and pull the cocking lever rearward one or more times to insure
the chamber is empty. Watch for a live round or empty case to
be ejected. Rotate the cocking lever upward slightly and lock it
into the indent in the cocking lever housing to lock the bolt
open.
• INSPECT CHAMBER – Inspect chamber for the presence of a
live round or empty case.
Visually – View chamber through open ejection port.
Physically –  Insert index finger through magazine well or
ejection port and feel for the presence of a round or cartridge
case in the chamber.
Remove any live rounds or empty cases from the chamber or
from within the firearm or magazine before handling the USC
further.
The HK USC carbine is now considered “Clear”.
WARNINGS
• Carefully read this operators manual before handling the
carbine.
• Only use the carbine after you have fully reviewed and 
understand these instructions.
• Observe all notes on handling and operation. Failure to do so
may result in injury or death of the operator or bystanders.
• Do not use any firearm if you have recently ingested alcohol or
drugs.
• When passing the carbine between persons, the weapon must
be clear and the bolt should be open.
• Always treat the carbine as if it were loaded and ready to fire.
• Never point the carbine at anyone during handling.
• Always point the carbine in a safe direction.
• Place your finger on the trigger only when your sights are
aimed at the target. 
						

							9
GENERAL
8USC CARBINE
Fig. 2   USC (right side view)
Fig. 3   USC oblique (rear, left side view)
General 
The USC Carbine is a semi-automatic small arm designed and
constructed according to the latest methods of advanced technology.
The upper receiver, magazine, lower receiver, and buttstock are made of
high strength polymer. The USC is a simple blowback operated weapon
with a fixed barrel capable of semi-automatic fire.
The USC offers maximum safety and accuracy as it fires from the closed
bolt position. The USC is easily disassembled into its main assembly
groups for cleaning and care without the use of tools.
Accessories 
The following accessories are available:
• mounting rails for aiming devices
• handstop
• multi-purpose carrying sling
• tactical lightsNOTE: Photographs throughout this manual show the USC carbine
with the accessory Picatinny rail mounted on the top of the upperreceiver.
Other accessories may also be available, please contact HK for more
information.
Fig. 1   USC (left side view)    
						

							11
DESCRIPTION OF ASSEMBLY GROUPS
10USC CARBINE
Assembly Group 1   Upper receiver with barrel 
The upper receiver is produced using fiber-reinforced plastics and
houses other subassemblies. The inside of the upper receiver contains
metal guideways for the bolt group as well as attachment points for the
lower receiver with magazine well and the buttstock.
The barrel is inserted into and pinned to the upper receiver. The cocking
lever of the carbine is located above the barrel. It also serves to
manually lock the bolt in its open position. The right side of the upper
receiver contains the ejection port.
The bottom part of the upper receiver includes the support bolts for the
lower receiver and a handstop with dual mounting points for the carrying
sling.
The sights are fastened to the top of the upper receiver. They consist of
a flip-up type rear sight with diopter (peep) and u-notch apertures as
well as of the front sight post with front sight hood. A Picatinny rail is
mounted on the top of the receiver. Six additional hard points are
molded into the receiver on the left, right, and on the bottom sides.
These hard points allow for the easy installation of additional rails.
Fig. 5  Upper Receiver with barrel and attachment components 
1 Upper receiver 5 Flip-up rear sight 
2 Barrel 6 Accessory Picatinny rail 
3 Front sight 7 Handstop
4 Cocking lever  8 Hardpoints
Assembly Groups
1 Upper receiver with barrel, folding buttstock and 
attachment components 
2 Bolt Group with recoil spring assembly, complete 
3 Lower receiver with trigger mechanism, backplate and
magazine well 
4 Buttstock with pistol grip
5 Magazine 
For accessories see pages 15-16
Fig. 4 USC Assembly Groups   
						

							13
DESCRIPTION OF ASSEMBLY GROUPS
Assembly Group 3  Lower receiver with trigger mechanism 
The lower receiver houses the trigger mechanism with ambidextrous
safety/selector levers, the magazine well, magazine release lever and
bolt catch. The forward portion of the lower receiver is hooked to the
upper receiver. The rear portion is fastened to the upper receiver using
guide rails in the pistol grip of the buttstock.
The safety/selector levers are fitted on both sides of the pistol grip.
The forward portion of the lower receiver has lugs for attachment to the
upper receiver. Behind these lugs is the magazine well with the
magazine release lever.
Above the magazine release lever is the bolt catch. It serves to hold the
bolt rearward when the last round is fired and to release the bolt from
the open position after an empty magazine has been replaced with a
loaded magazine.The rear side of the lower receiver includes the
integrated backplate with buffer and support for the recoil spring
assembly.
Fig. 10 Lower receiver with trigger mechanism and magazine well
1 Trigger 5 Bolt catch
2 Magazine release lever 6 Safety/Selector lever
3 Magazine well 7 Hammer
4 Attachment lugs 8 Trigger guard 
12USC CARBINEAssembly Group 2  Bolt Group 
The bolt group, together with the recoil spring assembly, is contained
inside the upper receiver. The reciprocal movement of the bolt group
provides for feeding and ignition of the cartridge, for extraction and
ejection of the spent case as well as for cocking of the hammer. The
right side of the bolt has a thumb recess for manual closing of the bolt
(forward assist).
The recoil spring assembly pushes the bolt forward into the firing
position. The cone-shaped support for the recoil spring assembly is
housed in the backplate of the lower receiver. The longitudinally
movable guide ring supports itself within the bolt.
The bolt group (Fig. 8 and 9) consists of:
1 bolt  5 firing pin retaining pin 
2 firing pin spring 6 recoil spring assembly, complete
3 firing pin assembly 6a guide ring
4 extractor 6b support
Fig. 8  Bolt Group, assembled 
Fig. 9  Bolt Group, disassembled    
						

							14USC CARBINE
15
DESCRIPTION OF ASSEMBLY GROUPS
Assembly Group 4  Buttstock with pistol grip
The buttstock is attached to the receiver by the means of two hex head
screws which can be installed or removed by using the HK tool.
Fig. 11  Buttstock with pistol grip
The buttstock holds the upper and lower receiver together. A rubber
cheek rest and buttplate are molded onto the polymer frame of the
buttstock.
Assembly Group 5  Magazine  
The magazine housing is constructed from plastic. The magazine
consists of: magazine housing, magazine floor plate, follower, follower
spring and locking plate.
Fig. 12  Magazine, complete         Fig. 13  Magazine, disassembled
1  Magazine housing 4  Follower spring
2  Magazine floor plate 5  Locking plate
3  Follower
safe                    semi-automatic fire   
The safety/selector lever of the USC trigger mechanism has two
positions :
Position    = Safe 
Position    = Semi Automatic fire        
						

							17
HANDLING & OPERATION
16USC CARBINE ACCESSORIES
Filling the Magazine 
• Grasp magazine.
• Slide individual cartridges under the magazine lips one by one (Fig. 20).
• Repeat this process until the required number of cartridges has been
inserted or the magazine is full (maximum 10 rounds).
Fig. 17  Filling the magazineNOTE: Loading more than the prescribed number of rounds will
prevent the magazine from being inserted in the weapon with thebolt forward.
Emptying the Magazine 
•Grasp magazine.
•With your thumb, push cartridges forward out of the magazine into the
palm of the other hand  
OR
•  Grasp magazine and hold it with the points of the bullets pointing
towards the bottom.
•  Use a piece of wood to slide the cartridges out of the magazine.
Insertion and removal of magazine 
•  Put the USC safety/selector on  (Safe).
•  Insert magazine into the magazine well (Fig. 18). The magazine catch
has to engage audibly in the process. Tug on the magazine to ensure
it is fully engaged.
•  For removal of the magazine, push magazine catch forward (Fig 19)
and remove magazine downward.
Fig. 18  Insert magazine Fig. 19  Remove magazine
Carrying sling 
The carrying sling (Fig.14) enables the shooter to carry the USC carbine
securely in a wide variety of positions.
Fig. 14  Sling
Cleaning Kit   The cleaning kit includes:
1 Transport case 5 Oil bottle  
2 Cleaning patches 6 Bore brush
3 Cleaning brush  7 Patch holder 
4 Cleaning rod with folding handle 
Fig. 15  Cleaning Kit
Mounting rails (MIL-STD-1913) for aiming devices 
The mounting rail (Picatinny Rail) is screwed onto the molded-in hard
points provided either on top of the receiver, below the forearm or on the
right or left sides of the forearm.
Fig. 16  Mounting rails        
						

							19
LOADING THE  USC
18USC CARBINE
Starting Situation 2: There is an empty magazine in the carbine.
The bolt is held back by the bolt catch.
•Put the USC safety/selector on  (Safe).
•Push magazine catch forward and remove empty magazine.
•Insert the filled magazine into the magazine well until the magazine
catch engages audibly. Tug to check.
•Depress upper end of bolt catch (Fig. 21), thus releasing the bolt and
allowing it to snap forward chambering a round.WARNING: The USC is now fully loaded and with the safety on.
FIg. 21  Depress bolt catch to release the bolt 
With heavy external fouling of the USC, (sand, sludge) or to load the
firearm quietly, the thumb recess on the bolt may be used as a forward
assist (Fig 25A). To do so use the thumb recess, push bolt forwards until
it is in the forward most position.
FIg. 22  Forward Assist 
Starting Situation 1: No magazine is present in the carbine. The bolt
is forward.
•Put the USC safety/selector on   (Safe).
•Insert the loaded magazine into the magazine well until the magazine
catch engages audibly. Tug downward to ensure it is properly seated.
•The USC is partially loaded and with the safety on.
•Pull cocking lever backwards as far as it will go and let bolt snap back
to its forward position chambering a round. In the process do not ride
the cocking lever forward.WARNING: The USC is now fully loaded and with the safety on.
or•Pull cocking lever backwards as far as it will go, (Fig. 20 ) and swivel it
upwards (engage it in the indent) into the open position.
•Insert the loaded magazine into the magazine well until the magazine
catch engages audibly. Tug to check.
•With the open palm of the non-firing hand slap the cocking lever
downward and forward to chamber a round. During this process do
not ride the cocking lever forwards.WARNING: The USC is now fully loaded and with the safety on.
FIg. 20  Pull cocking lever backwards