MK23 Mod 0: The Crew-Served Pistol

MK23 Mod 0: The Crew-Served Pistol


Due to H&K having already embarked on a new advanced family of weapons they had several legs up on Colt.  Colt, due to the time constraints, for all intents and purposes threw their OHWS submission together using preexisting technology.  They combined the M1911 with features from the Double Eagle and the locking system of their failed All American 2000.  The frame was basically an M1911 type frame with a longer grip to accept the 10-round single column magazine.  The decocking mechanism was taken from the Double Eagle while retaining the cocked and locked safety of the M1911.  Colt chose the rotating barrel locking system of the All American 2000.  This proved problematic since you could not attach a suppressor directly to the barrel as the pistol could not function.  To deal with this, a separate mounting apparatus was used that attached to a rail in front of the handguard where the suppressor was attached.  Colt engineers did not necessarily agree this was the best method but due to time constraints they were limited on what they could design as well as test.  This is not saying that if Colt would have had more time the outcome would have been different; however Colt has not then nor since put out a handgun that would have been suitable for the requirements set out in the RFQ.  Early on in the planning of the requirement, SOCOM said they did not want an M1911 variant and for the most part that was what they got with the only difference being the barrel locking system. When looking at the requirements SOCOM had, H&K was already working on a new pistol which already had many of those characteristics.

The MK23 breaches the two worlds of combat reliability and match grade accuracy. This is a very difficult task but was accomplished by H&K with this pistol.

In January 1993, H&K introduced their new family of weapons with the acronym USP or Universal Self-loading Pistol.  The first pistol was based on the newly released .40 S&W caliber cartridge. This was a wise move due to the fact that the new caliber was more powerful than the 9mm and the new pistols chambered in this caliber were basically 9mm caliber pistol chambered for the new caliber.  Many of the newer .40 caliber pistols being developed by other companies suffered durability and longevity issues.  The USP 40 was in fact the first pistol designed around this new caliber and then modified to take the less powerful 9mm caliber.  In 1995, H&K would release for the commercial market their UPS 45 chambered in the .45 Auto caliber pistol.

Compared to anything else on the market, the USP was in fact the most advanced handgun design available.  It took the advancements of the polymer frame which H&K had extensive background going back to the 1970s with the P9S and VP70Z and gave the customer the double/single action features they wanted and a few more advancements as well.  The pistol used a conventional short recoil operation utilizing a modified Browning-type link-less system.  The frame was entirely made of a polymer called polymide, which is very light and very strong.  The magazine release was ambidextrous and the magazines were drop free and also made of polymide.  One strange departure was the original USP pistols did not use H&K’s trademark polygonal rifling but used a conventional lands and grooves system.  This would not take long to change; the H&K customers demanded the barrels H&K was famous for.  Perhaps the feature that stood out the most and contributed significantly to increasing service life and reducing recoil (30% less recoil) was the patented recoil reduction mechanism.  Basically, there are two recoil springs, one that returns the slide forward and one that cushions the impact of the slide into the frame.  This is also what makes the pistol shoot high pressure ammunition with little to no consequence.  The USP is offered in 10 variants that include double/single with a manual safety, decock only, cocked and locked, and double action only and the pertinent in left hand variations as well.  The variant 8, the “missing variant” is a U.S. government test sample, essentially a variant 7 double action only.

Shown is a Phase two MK23 during its testing phases. The MK23 is available to any unit that falls under the umbrella of SOCOM. (Heckler & Koch)

The MK23 started with the USP concept and in fact shares most of the features with some modifications made that were mandated in the RFQ.  The MK23 maintains the passive firing pin block of the USP that requires the trigger to be pulled all the way to the rear before the firing pin is released to strike the primer.  There is a separate decocking lever that allows the pistol to be decocked quietly as well as a thumb safety that can be used if the operator chooses to carry cocked and locked.  The MK 23 has an overall length of 9.65 inches.  The pistol weighs 2.66 pounds empty.

The frame of the MK23 is manufactured from the same polymide as the USP but a larger frame with an oversized trigger guard to accommodate heavy gloves.  Due to the requirement for a laser aiming module a rail was added to the front of the frame.  The trigger guard is flared to the rear to protect the wings of the ambidextrous magazine release from accidental release of the magazine.  When comparing the Phase 1, 2 and 3 H&K pistols you are able to see where modifications have been made as the process went on such as the elimination of the slide lock (so no slide chatter is heard when firing suppressed) that was used on the phase 1 pistol only, change in the checkering on the front and backstrap of the pistol.  There were gripping grooves on the front of the slide on Phase 1 and 2, which were eliminated on the final version.

The slide is manufactured from a single piece of steel.  The main evolutionary changes in the slide was the omission of forward gripping notches, which were used on Phase 1 and 2 pistols only.  Modifications had to be made to the sights due to the large diameter of the sound suppressor.  The sights had to sit up higher so they could be used when the suppressor was installed.  The sights chosen were tritium night sights.  All of the roll pins are nickel plated to insure against corrosion as well as the firing pin.  The finish is very unique.  It is a lacquer appearing black finish, which is a proprietary maritime finish intended to protect the pistol from salt water emersion and has been tested in salt/fog spray chamber lab testing up to 96 hours.  This pistol again was intended for surf and ocean conditions a SEAL would encounter in his mission.  This finish is a three step process beginning with the bare slide being nitrocarborised, second phosphate and coating of the black lacquer to give it the black appearance.  Even if the black surface finish is worn off, the slide is still protected.

Shown is the commercial MARK23 with the Insight Technology LAM (Laser Aiming Module).

The barrel, like all other H&K weapons, is manufactured from a cold hammer forging proceeded with polygonal rifling.  This rifling has no sharp edges to wear and sports a tighter diameter than a standard barrel providing a better and stronger bullet to bore seal.  With no sharp edges there is nothing to wear increasing the barrel life.  On top of this, the 6 land and groove bore is chrome plated to further increase life as well as corrosion resistance.  The barrel is threaded to accept the sound suppressor and as fitted with a rubber “O” ring that helps to lock the barrel to the slide consistently the same to increase accuracy.  This greatly assists in the pistol being able to maintain the requirement of 2 1/2 MOA at 25 yards when in actuality the MK23 far exceeded the requirement with 1.44 inches with many groups under 1 MOA.

The operation requirements for this pistol, it is safe to say the standards for the OHWS, were by far the strictest and most stringent of any pistol in the world.  During Phase 2, the reliability testing could not fall below 2,000 mean rounds between failure. The MK23 averaged around 6027 mean rounds between failure and a maximum of 15,122 rounds between failures far exceeding the requirement.  Three pistols were subjected to endurance testing of 30,000 rounds each and after the testing was concluded the pistols maintained the original standard of 2 1/2 inches at 25 meters.  The only part needed replacing was the runner “O” ring which has a service life of 20,000 rounds.  Environmental testing was nothing short of brutal requiring the weapon to function in temperature ranges from -25ºF to 140ºF.  On top of that was the sat fog spray, covered in mud, frozen in ice as well as sand testing. Most of the testing was conducted with no lubrication on the pistol.

The MARK23 provided was tested with Pierce Ammunition .45 Auto 230 grain FMJ. This target showed a 1 1/4 inch group at 25 meters. The MK23 breaches the worlds between combat reliability and match accuracy – a very difficult task to accomplish.

The sound suppressor was part of the RFQ and part of the OHWS.  The Phase I sound suppressor was manufactured by H&K.  However, the Phase II and III suppressors were manufactured by Reed Knight at Knight’s Armament Company.  Though a hard pill to swallow, H&K knew that the KAC suppressor was far superior to theirs not to mention it was the one Colt went with.  The KAC OHWS sound suppressor was designed by Doug Olson who is probably one of the most noted suppressor designers in the industry.  The suppressor is manufactured from stainless steel with a Moly resin finish and 1.37 inches in diameter. The service life is an impressive 15,000 rounds.  Of course with proper maintenance that number can be much greater.  KAC uses the most state-of-the-art robotic welding and wired EDM process to insure gun-bore-to-baffle alignment followed by heat treat/stress relieve.  This suppressor will not affect the reliability or accuracy of the pistol.  The suppressor delivers more sound suppression if the inside of the suppressor has 5 cc of water in it; this creates additional turbulence thus more sound reduction (dry the suppressor reduces 26 dbs, wet the suppressor reduces 36 dbs).  The suppressor also works as a very effective flash suppressor as well by reducing muzzle flash by 90% using ball ammo.  The suppressor was designed to overcome the normal issue of the weight of the suppressor slowing down the slide velocity which, in semiautomatic short-recoil operated pistols, cause’s malfunctions.  This was overcome by Olson designing a hollow piston in the rear of the sound suppressor.  There is a heavy captive spring surrounding the piston, which is held in place by a threaded retaining ring.  The baffles are located in the main suppressor body.  What this spring loaded piston does is when the pistol is fired the expanding gases that drives the projectile enters the suppressor and cause over pressure in the suppressor which in turn drives the suppressor body forward and then drives the piston rearward.  Due to the suppressor being screwed onto the end of the barrel, it gives the pistol an extra jolt to the rear.  This completely alleviates the issues related to slide deceleration.  An additional feature of the suppressor is the ability to adjust the point of impact of the projectile.  This is accomplished by having at the rear of the suppressor 10 squared off teeth that lock in with squared off teeth on the pistons cap spring.  The suppressed group is moved by rotating the suppressor body one tooth after the other.  The position that provides the least suppressed to un-suppressed point of impact difference is recorded. Once this setting is found it never needs to be changed.

The MK23 has a decocking lever on the left side as well as a manual safety enabling the pistol to be carried with the hammer in the cocked position. This lever is ambidextrous.

The third component to the OHWS is the LAM or Laser Aiming Module.  This is manufactured by Insight Technologies.  Weighing only 5 ounces, the LAM features a 620 to 650nm visible laser sight that can be manually adjusted to zero at the range of the operator’s choosing.  There is a 70 lumen halogen bulb as a light source and third is a 810 to 850nm infrared laser.  This is used in conjunction with night vision glasses.  This would enable an operator to engage targets in total darkness accurately and reliably.  The LAM is operated with two DL123A 3V batteries.  There is a dial on the left side of the LAM that allows any combination of the features to be used.  There is an activation lever that is ambidextrous under the unit and rests under the trigger guard where it is easily activated by the operator.

On June 8, 1995, H&K was awarded the contract for the USSOCOM pistol and designated the MK23 Mod0 (NSN 1005-01-426-8951).  All pistols were manufactured in Germany.  On May 1, 1996, the first MK23 pistols were delivered to SOCOM for operational use.  Unfortunately, the MK23 program was less than a success although through no fault of the pistol.  Due to the size and weight, many of the new operators were brought up with the double tap 9mm training.  Carrying more ammunition in a lighter handgun they learned to compensate for the pistol’s shortcoming by firing an extra shot.  Most of these newer operators had little to no combat experience to see the real downfalls of the 9x19mm caliber and to see how effective the .45 Auto caliber really was.  Additionally, H&K introduced the USP 45, which sported most of the same features in a lighter and smaller package.  Strong political pressure inside the services at the time worked against the fielding of the MK23 to the Army and Air Force.  These factors greatly contributed to the lack of production of both the pistol and the new +P ammunition.  In the nearly decade wars in both Afghanistan and Iraq, the younger generation operators saw firsthand the superiority of the .45 Auto caliber handgun over the 9x19mm one.  Special Forces had pulled the MK23 out of storage as well as bought more USP 45s, Glock 21s as well as M1911-type pistols.  The MK23 is truly an amazing handgun.  Bridging the worlds between combat reliability and match accuracy is nearly impossible: but H&K did it.

The MK23 is a combat reliable but match grade accurate pistol. Shown is the pistol field stripped. Notice the recoil spring guide, which has the proprietary H&K recoil reduction system. This reduces both recoil and stress on the frame.

H&K offered this state-of-the-art to the commercial market as the Mark 23 pistol.  The first models offered were the exact same pistol with the only change being its SAAMI spec chamber.  They came with the maritime finish and even a surface finish information card notifying the customer that this finish was “not designed or selected for aesthetic beauty.”  It is a functional finish designed specifically to protect the weapon from maritime conditions.  Later commercial pistols would use the same finish as the USP.  Currently H&K still offers the Mark23 in their catalog.

The test and evaluation pistol provided for this article was a later production MARK23.  The ammunition used to test fire this pistol was Pierce Ammunition .45 Auto 230gr Ball ammunition.  Pierce Ammunition is located in Buffalo, New York and manufacture match grade, military and commercial ammunition.  They also will provide custom loads for customers per their specifications or develop a load for a special application.  Every round is optically inspected to guarantee the best possible ammunition.  More than 500 rounds were fired through the pistol with no malfunctions of any sort.

The MK23 is truly in a class of its own.  No handgun in the world has ever been through such rigorous testing and came out on top.  Most handguns would be metal scraps after half the testing this pistol went through.  Many operators could not wrap their heads around the size and the fact this was an offensive weapon and not a sidearm.  Perhaps if this was better understood the pistol would have been used more widely.  But there is no question the OHWS program was a big success on the mechanical side.  It was the political and culture ends that were the programs demise.