Heckler And Koch HK Mark23 Operators Manual

							1 CONTRACT NUMBER N00164-94-C-0040SW370-BD-OPI-010
Operator’s Manual
Mark 23 Pistol, Semi-automatic,
Caliber .45 ACP
© Heckler & Koch, Inc., October 1996
21480 Pacific Blvd.
Sterling, Virginia  20166-8903
United States of America
Telephone (703) 450-1900
®
WARNING
A firearm has the capability of taking your life or the life of someone else! Be extremely careful with your
firearm. An accident can occur at anytime and is almost always the result of not following basic safety rules. 
						

							2
TABLE OF CONTENTS
PAGE
CHAPTER 1 INTRODUCTION..................................................................................................................................................... 4
SECTION I GENERAL INFORMATION........................................................................................................................................ 4
SECTION II PISTOL DESCRIPTION............................................................................................................................................ 6
1.2  Nomenclature................................................................................................................................6
1.3  Principle of Operation.................................................................................................................. 7
1.4  Major Assembly Groups............................................................................................................... 7
1.5  Technical Specifications............................................................................................................... 9
CHAPTER 2 OPERATING INSTRUCTIONS............................................................................................................................. 10
SECTION I SERVICE UPON RECEIPT OF MATERIAL........................................................................................................... 10
2.1  Initial Inspection......................................................................................................................... 10
SECTION II GENERAL DESCRIPTION.................................................................................................................................... 10
2.2  Description.................................................................................................................................. 10
2.3  Operation and Characteristics................................................................................................... 11
2.4  Cycle of Operation..................................................................................................................... 13
2.5  Safety Features.......................................................................................................................... 17
SECTION III OPERATION UNDER NORMAL CONDITIONS.................................................................................................. 18
2.6  Clearing Procedures.................................................................................................................. 18
2.7  Loading and Unloading the Magazine....................................................................................... 19
2.8  Loading Procedure..................................................................................................................... 20
2.9  Readying the Pistol for Firing.................................................................................................... 21
2.10  Firing the Pistol........................................................................................................................ 22
SECTION IV OPERATION UNDER UNUSUAL CONDITIONS................................................................................................ 23
2.11  Extreme Cold............................................................................................................................ 23
2.12  Hot, Wet Climates.................................................................................................................... 23
2.13  Hot, Dry Climates..................................................................................................................... 24
2.14  Heavy Rain and Water Operations - All Climates................................................................... 24 
						

							3
SECTION V MALFUNCTIONS AND STOPPAGES.................................................................................................................. 25
2.15 Remedial Action........................................................................................................................ 25
CHAPTER 3 MAINTENANCE INSTRUCTIONS....................................................................................................................... 27
SECTION I TOOLS & EQUIPMENT.......................................................................................................................................... 27
3.1  Operator Tools and Equipment Required.................................................................................. 27
SECTION II PMS CHECKS & MAINTENANCE PROCEDURES.............................................................................................. 27
3.2  General....................................................................................................................................... 27
3.3  Disassembly (Field stripping)..................................................................................................... 28
3.4  Reassembly (From field strip).................................................................................................... 30
3.5  Safety/Function Check............................................................................................................... 33
3.6  Function Firing............................................................................................................................ 36
3.7  Cleaning..................................................................................................................................... 36
3.8  Inspection................................................................................................................................... 37
3.9  Lubrication.................................................................................................................................. 38
SECTION III ADJUSTMENT OF SIGHTS................................................................................................................................. 40
SECTION IV TROUBLESHOOTING PROCEDURES............................................................................................................... 43
3.10  Operator Troubleshooting Procedures.................................................................................... 43
3.11  Parts Listing and Exploded Diagram....................................................................................... 46
CHAPTER 4 AMMUNITION....................................................................................................................................................... 48
FIREARM SERVICE RECORD...................................................................................................................INSIDE BACK COVER 
						

							4
CHAPTER 1   INTRODUCTION
SECTION I - GENERAL INFORMATION
The HK Mark 23 .45 ACP pistol give shooters match
grade accuracy equal to that of the finest custom made
handguns — yet it exceeds the most stringent operational
requirements ever demanded of a combat handgun.
The Mark 23 provides this accuracy without the need for
hand-fitted parts common in custom-built match pistols
costing thousands of dollars more. Repair of the Mark 23
is reduced to a simple parts exchange.
The HK Mark 23, is a commercial model of the U.S.
Government issue MK 23, MOD 0 pistol and is available
in limited numbers. Designated the “Mark 23”, it is almost
identical to the MK 23, MOD 0 pistol used by the Special
Operations Command, right down to its threaded barrel.
The main differences are slide Markings (Mark 23 as
opposed to MK 23) and a barrel manufactured to SAMMI
headspace specifications.
One of the most thoroughly tested handguns in history,
the MK23/Mark 23 project originated in 1991 when HK
was awarded a development contract for the SpecialOperations Forces Offensive Handgun Weapon System,
consisting of a caliber .45 pistol, detachable sound and
flash suppressor, and laser aiming module (LAM).
During testing, MK 23 pistols met the most stringent
operational and accuracy requirements ever demanded of
a combat handgun. MK 23 pistols achieved match grade
accuracy of less than a 2.5 inch maximum extreme
spread in 5-round shot groups at 25 meters with service
ammunition. Endurance testing demonstrated a service
life of over 30,000 rounds of +P ammunition with no parts
breakage, with an additional 30,000 rounds certified on
the slide and frame.
To meet the reliability requirement, the pistol had to
demonstrate a minimum of 2,000 mean rounds between
stoppages (MRBS) with both M1911 ball and +P
ammunition. The minimum MRBS achieved in testing was
6,027 and the maximum was 15,122!
During over 450 accuracy test firings from a precision
firing fixture, MK 23 pistols far exceeded the government
requirement, averaging 1.44 inches, with 65 groups of
less than one inch. There were four groups of .5 inches,
with 5 rounds going through the same hole! This included
firing with and without the sound/flash suppressor
attached. 
						

							5
Three pistols were tested for accuracy after firing over
30,000 rounds, the specified service life of the pistol, and
still met the new pistol accuracy requirement. An
innovative design feature, a high temperature rubber O-
ring on the barrel that seals the barrel in the slide until
unlocking, led to this remarkable achievement. The O-ring
lasts beyond 20,000 rounds and can be replaced by the
operator without tools in seconds.
To meet operational environmental requirements, the
pistol was function tested at +140 and -25
0 F, immersed in
salt water, exposed to surf, salt-fog, sand-dust, mud,
icing, unlubricated, and a variety of other fouled
environments. A special maritime surface coating protects
the pistol from corrosion, in all of these operational
environments.
The barrel is threaded to accept accessories such as a
flash and sound suppressor. The unique HK polygonal
bore profile increases muzzle velocity and service life,
reduces bore fouling and eases cleaning.
The frame mounted MK 23 decocking lever is separate
from the ambidextrous safety lever. It allows the hammer
to be lowered quietly and safely from the single action
position. When the hammer is down, the ambidextrous
frame mounted safety lever is locked in the fire position
so that the pistol is always ready for double actionoperation. When the hammer is “cocked and locked” in
single action mode with the safety lever on “safe”, the
decocker is blocked so that the pistol is always ready for
single action operation. Even with the safety lever
engaged, the slide can still be manipulated to load and
clear the pistol.
The extended slide release lever and the ambidextrous
magazine release are easily operated without adjustment
of the firing grip using the firing hand thumb or index
finger.
Other notable features include accessory mounting
grooves on the frame, a mechanical recoil reduction
system that reduces recoil forces to the shooter and
components of the pistol by as much as 30%, a polymer
frame, a one-piece machined steel slide, and a law
enforcement/military magazine capacity of twelve rounds.
The weapon is aimed using either iron sights or an
optional laser aiming component. The iron sights provide
a 3-dot sight picture with white or optional self-luminous
tritium dots.
The MK 23 became the first caliber .45 ACP pistol to
enter U.S. military service since the venerable
Government Model 1911A1. On May 1, 1996, the first MK
23 pistols were delivered to the U.S. Special Operations
Command for operational deployment. 
						

							6 SECTION II - PISTOL DESCRIPTION
1.2  Nomenclature
Figure 1  Left View
1.3  Principle of Operation
A. The Mark 23 uses a modified linkless Browning-
style short recoil system to lock and unlock the
breech.
Figure 2  Right View
B. Upon firing, the pressure developed by the
propellent gas forces the slide and barrel
assembly to the rear. After approximately 3 mm,
the locking block will stop the rearward
movement of the barrel as the barrel is pivoted
downward due to the engagement of the angled
surfaces of the locking block with those located
rear sight
right
safety leverextractorbarrel locking
blockfront sight
ejection
port
accessory
mounting
groove slide release
axle recess
trigger
magazine
release
lanyard loop
sliderecess for slide
release/stop
slide release
magazineframe accessory
mounting
groove
magazine
releasedecocking
lever left safety
lever
threaded insert
for accessory locking
flared
trigger guardhammer
threaded barrel 
						

							7 in the recoil spring guide rod. The locking block
will disengage from the slide and the slide will
continue rearward.
The extractor located in the slide will then
extract the fired cartridge case, the ejector
located in the frame on the left side of the
magazine well will eject the fired case as the
slide continues rearward and cocks the
hammer, and compresses the recoil spring.
The slide moves forward feeding the next
cartridge from the magazine into the chamber
and  locking to the barrel breech.
C. The slide locks open after the last round has
been fired and ejected.
 WARNING
Do not rely on the slide lock to determine if
the magazine is empty. Always check visually
and physically ensure the pistol is not loaded.
1.4  Major Assembly Groups  (See Figure 3)
A. Slide - houses the firing pin, firing pin block andextractor; cocks hammer during recoil.
B. Captured Recoil/Buffer Spring Assembly
(with guide rod) - absorbs recoil and returns
the slide and barrel to their forward positions;
reduces  impact of slide on receiver during
recoil. The recoil spring is “captured” by a C-clip
on the end of the guide rod.
C. Threaded Barrel (with locking block) -
contains cartridge and propellent gases during
firing.  The locking block initiates locking and
unlocking of the breech during movement of
slide. The O-ring holds the barrel tight in the
slide until unlocking.
D. Frame -  serves as support to all major
components; controls functioning of pistol. The
slide release locks the slide with barrel and
recoil/buffer spring assembly to the metal
locking insert cast into the synthetic frame. A
lanyard loop is in the bottom of the grip for
attaching a lanyard. The trigger guard is flared
on both sides to preclude accidental actuation
of the magazine release during holstering. 
						

							8 E. Magazine -  holds the cartridges in position for
feeding and chambering.F. Slide Release - holds slide to rear when
engaged;  releases slide when lever is
depressed.
Figure 3  Major Assembly Groups
A. Slide
C. Threaded
Barrel
D. FrameE. Magazine
F. Slide Release accessory
mounting groove
threaded insert for
accessory lockingO-ring
threadsbarrel locking block
flared trigger guard
lanyard loop insert
C-clipguide rodrecoil springbuffer springB. Captured Recoil/Buffer
Spring Assembly
safety
magazine
releasedecocker 
						

							9 1.5  Technical Specifications:
Caliber .45 ACP (Automatic Colt Pistol)
System of Operation short recoil, semi-automatic
Locking System Browning system (modified), linklessLength Barrel 5.87 in. (149 mm)
Sight radius 7.76 in. (197 mm)
Pistol 9.65 in. (245 mm)Weight Magazine (empty) 12 or 10 rd. capacity .24 lbs. (.110 kg)
Magazine (w/12 rds M1911 Ball) .81 lbs. (.366 kg)
Magazine (w/10 rds M1911 Ball) .72 lbs. (.327 kg)
Pistol (w/ empty 12 or 10 rd magazine) 2.66 lbs. (1.21 kg)
Pistol (w/ 12 rds M1911 Ball) 3.22 lbs. (1.46 kg)
Pistol (w/ 10 rds M1911 Ball) 3.13 lbs. (1.42 kg)Trigger Pull Single-action 4.85 lbs. (2.20 kg)
Double-action 12.13 lbs. (5.50 kg)Height 5.90 in. (150 mm)
Width 1.53 in. (38.8 mm)Muzzle velocity M1911 230 grain ball 886 fps (270 m/s)
+P 185 grain JHP 1142 fps (348 m/s)
Maximum Effective Range 54.7 yds (50 m)
Maximum Range (M1911 ball) 1,467 yds (1,341 m)Rifling polygonal bore right hand twistMagazine staggered, 12 round capacity (10 round civilian)Safety Features 1. safety lever (manual), 2. double-action mode with 12.1 lb. trigger
pull, 3. firing pin block, 4.  disconnector 
						

							10SECTION II - GENERAL DESCRIPTION
2.2  Description: The Mark 23 is a semiautomatic,
magazine fed, recoil operated, double/single-action
pistol, chambered for the .45 ACP cartridge up to,
and including, the commercial +P cartridges.
WARNING
The Mark 23 incorporates single and double
action modes of operation. Anytime the trig-
ger is pulled with the safety lever in the fire
(down) position and a round in the chamber,
the pistol will fire from either the hammer
down (DA) or cocked position (SA).
CHAPTER 2   OPERATING INSTRUCTIONS
SECTION I - SERVICE UPON RECEIPT OF MATERIAL2.1 Initial Inspection. Upon initial receipt, the pistol
is to be inspected to ensure it was received in
proper working order.Step
Action
Reference
1 Remove pistol and items
from container
2 Remove packing material
3 Check for missing items
4 Field strip weapon and
inspect for: para. 3.3
  Missing parts
  Proper assembly
5 Clean, dry and lubricate
  (if necessary) para. 3.7, 3.9
6 Assemble para. 3.4
7 Safety/ function check para. 3.5