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MK 23 SUPPRESSOR DEVELOPMENT: THE TRANSITION FROM THE COLT TO THE H&K PISTOL

Your faithful correspondent recently had the opportunity to view the genesis of the Offensive Handgun Suppressor by Knight’s Armament Company (KAC). While there is much talk about the newly adopted suppressor and its amazing performance, little is ever shown of exactly “What” makes it function so well. The new system adopted by USSOCOM was an engineering challenge of the first order, and KAC spent over $250,000 and 18 months in the development process. SAR contributor Doug Olson was Chief Engineer on the project, and I managed to talk him into telling the story himself. We hope you enjoy this SAR exclusive look not only into this amazing suppressor, but the intense process that goes into filling a U.S. government firearm procurement.

The development of the Suppressor for the Mk 23 USSOCOM Pistol was a huge challenge. The U.S. Government’s desires for the Suppressor’s performance far exceeded anything that had ever been accomplished commercially. The initial development contracts were released in 1991: one to Colt’s Firearms with Knight’s Armament developing the suppressor and one to H&K with their own suppressor design. The state of the art at that time was the Qual-A-Tec/AWC Technology produced Nexus 45 for the M1911 Colt. That 1991 suppressor only delivered approximately 18db reduction, wet. That was a long way from the 30db dry that the Government was seeking. KAC went through a 12-month development process that resulted in delivery of suppressors for the Colt OHG that in Government tests averaged 28.8db reduction with M1911 ball and 26.6db reduction with +P. The H&K suppressor averaged 22.2db reduction with M1911 ball and 15.2db with +P. That was only part of the story because the KAC suppressor yielded an incredible 36db reduction when water was added to the suppressor. It was obvious why the Government wanted to have the KAC suppressor attached to the superior H&K weapon. That was a very impressive advance in the state-of-the-art in a relatively short time frame.

The Government initially decided that surely KAC could easily convert the design from the Colt’s Pistol to the H&K Pistol with no additional development expenditure and thus decided it would not fund any additional development effort. That erroneous situation was finally corrected and late in 1994 KAC was issued a contract to change its suppressor design to fit the H&K weapon.

The task proved to be a more formidable challenge then even KAC had anticipated. The suppressor for the Colt pistol was attached directly to the frame of the weapon. That meant that the Suppressor for the Colt pistol did not need a booster to force the weapon to function with the additional weight of the suppressor. The job was now to adapt the suppressor to a gun that required a booster, while keeping the performance of the original suppressor.

One area of the suppressor that many still do not understand is how the recoil regulator (booster) works. This is sometimes referred to as a “Nielsen device”. Based on many years of experience with the system, the following will try to explain its function. If one were to mount a conventional suppressor to the barrel of a pistol that uses a short recoil mechanism (like the M1911 or H&K OHG) one would immediately find that the weapon would not cycle semi-automatically. That is because the suppressor mass was added to that of the barrel and slide putting the total mass beyond the design limits of the gun. One could of course reduce the mass of the barrel and slide and change the recoil spring to achieve proper functioning with the suppressed pistol. The problem would be shifted to cycling of the converted pistol without the suppressor. The low slide and barrel mass would result in increased velocities of the parts and the gun would have a greatly reduced service life and increase the risk to the shooter of the slide coming off the back of the gun after firing. Neither of these situations is acceptable.

What then is the solution? It is to allow the mass of the suppressor to move independently of the barrel and slide until after the slide is unlocked from the barrel. A piston is added to the back of the suppressor that attaches to the barrel. The suppressor is thus allowed to move forward along the axis of the piston against a spring load. The propellant gasses that enter the suppressor work to apply a force to the piston head tending to drive it along with the barrel and slide to the rear while driving the rest of the suppressor forward. This “equal and opposite reaction” against the barrel makes the weapon function more or less normally.

What must happen is that the suppressor must reach the end of its stroke AFTER the barrel becomes unlocked from the slide. It is easy to imagine the shock that the barrel sees when the suppressor reaches the end of its stroke. As they say “timing is everything”. Much work was done to make sure the suppressor matches the weapon to provide for equal weapon life with and without the suppressor. Hundreds of thousands of rounds were fired throughout the development and test cycles of the weapon and suppressor.

That also means that a recoil regulator for one type of weapon may not work on another type. That was exactly the situation KAC ran into with trying to adapt the OHG Suppressor onto the smaller H&K USP and Glock pistols. The relative slide and barrel mass of these weapons was, from a dynamics standpoint, very different from that of the OHG. The Tactical pistol’s slide only lived 300 rounds when the OHG suppressor was first tested on the gun. To prevent that from happening, H&K changed the barrel threads from right hand to left hand to prevent the OHG suppressor from inadvertently being fired on the Tactical gun. H&K ran an exhaustive test and developed a special modification to the piston, regulator spring and buffer that provided proper functioning with the Tactical. KAC has built its commercial Tactical suppressors with those modifications and even with springs provided by H&K. It is of note that very few rounds fired from the wrong regulator setup can ruin a gun. It is also interesting to note that the lighter slide and barrels reduces the efficiency of the suppressor and results in a sound pressure level reduction of 3db less.

One of the problems the first generation H&K suppressor displayed was that it loosened from the barrel. When this happened bullet strikes were noted inside of the suppressor and accuracy was lost. The culprit was traced to the barrel to suppressor interface. The interface for the suppressor onto the barrel had to be changed to provide for additional stability. The first generation H&K OHG had threads at the end of the barrel with a single diameter behind the threads to support and align the suppressor. KAC had the interface changed to have two bearing surfaces, one behind the threads and one in front of the threads that provided support at both ends of the interface. Because the pistol itself was so long, H&K could not allow any more length of engagement between the suppressor and the barrel. That meant that the allowable tolerance with which the two diameters on the barrel and the two bores within the piston had to be reduced to keep the allowable misalignment at the end of the suppressor to acceptable limits. Both bores within the piston ended up with +/- .0005 tolerances. It also means that the threads no longer provided any alignment, they simply held the two parts together. An “O” ring was added within the piston that engages the front diameter on the barrel. It acts as a friction device to help keep the suppressor tight onto the barrel. The dual diameter support helps keep the alignment of the suppressor to the barrel even when the suppressor is not tight on the barrel.

When KAC first started to adapt its Suppressor for the Colt OHG to the H&K gun, one of the challenges was to make a piston for the recoil regulator to have geometry similar to the muzzle support for the Colt gun. Contrary to the initial looks, the muzzle device for the Colt gun was designed to be an effective component of the suppressor and not to be any thing special from a muzzle brake design. That muzzle device was responsible for bringing down the sound pressure level of the suppressor by a full 3 db over a straight interface.

The initial suppressor prototypes were fitted to first generation H&K guns and in order to keep the muzzle brake interface as close as possible KAC tried to move the recoil regulator springs to the outside of the can. At first it was thought that four small springs would work, then six, then ten. The small diameter and short springs just too severely limited the stroke of the piston and were finally abandoned. Moving the spring to the inside of the can exposed it to all of the contamination and heat from the propellant gas but there was no option since KAC had to keep within the size limits imposed. The piston, spring and buffer designs all went through a number of iterations before a final design was found that provided acceptable sound pressure level reduction and had proper service life.

Small changes such as increasing the length of the piston where it engages the bore of the suppressor were found to be necessary to allow easy removal and reinstallation of the piston. Since the overall length of the suppressor could not increase and the stroke of the piston could not decrease, the longer piston bearing resulted in a reduction in the total length of the baffle stack. The shorter baffle stack of course reduced the net efficiency of the can. In all the baffle stack had to be shortened by approximately 1/2 inch from that of the Colt pistol to keep the system overall length within the specification. Certainly a quieter suppressor could have been delivered if the length of the can could have been increased. On the commercial side of the suppressor business limits like this are seldom imposed. Designing a suppressor to meet a Government Specification can present a great challenge.

Another problem that KAC accidentally found was that the H&K Pistol would not tolerate any interference between the suppressor and the recoil spring guide rod. The problem is that static measurements do not show the true situation because the recoil spring assembly has a secondary buffer spring. Under dynamic loading, the guide rod can protrude further from the weapon in full recoil than was obvious when taking static measurements. What happened was the suppressor on its return to battery would just tap the end of the guide rod. That tap resulted in a broken slide. Hard to believe? We thought so too, but it happened. The dynamics of this system must be understood to achieve long weapon life.

The end result, the MK23 Suppressor, has set a new standard in suppressor technology. It has been tested with more rounds than probably any other suppressor ever built. At the 1997 Suppressor trials at Knob Creek it produced an unheard of 42db reduction with a little water in the tube (wet). That is quieter than many of the 22 caliber suppressors that were tested. The problem is we know it could have been even quieter had KAC been allowed a little more volume. But the user (USSOCOM) has an excellent piece of hardware that will see service for many years to come.

Knights Manufacturing Company

Dept. SAR
7750, 9th Street S.W.
Vero Beach, FL 32968
(561)778-3700 – Phone
(561)569-2955 – Fax

I would like to express my sincere appreciation to Mr. Jim Schatz of Heckler & Koch, Inc., without whose assistance this
article would not have been possible.

Heckler and Koch’s Universal Self-Loading Pistol, better known as the USP, is a true firearms success story in what has become a highly competitive worldwide handgun market. In order to succeed in this arena, a handgun must not only meet the criteria for which it was designed, but must actually exceed most of them. In essence, a good firearm is synergistic – it is greater than the sum of its parts. The USP is such a pistol. It combines the best of traditional firearms with the best of state of the art firearms technology. While not as widespread in police use as Glock pistols, the USP is nonetheless just as reliable, while being much more flexible in its ability to be modified to meet specific user requirements. Moreover, the USP is a traditional pistol in the American idiom, while at the same time taking full advantage of the most modern materials to achieve levels of reliability and longevity that would have been unimaginable just 25 years ago.

The genesis of the USP can be traced to the “Miami Shoot-out” which caused the Federal Bureau of Investigation to change from 9mm Parabellum to 10mm. H&K wanted to compete for the FBI 10mm pistol contract, but had no pistols in 10mm caliber, nor any conventional double action/single action (DA/SA) pistol as required by the FBI specifications. In fact, H&K had no pistols other than in 9mm caliber and the company came to realize that if it was to maintain its viability in an increasingly competitive handgun market, it would have to expand and diversify its product line. Moreover, management realized that as good as their pistols were, several, such as the P7 were unconventional, although most people who purchase handguns are essentially conservative, preferring more conventional designs. Further, Heckler & Koch realized that P7 pistols for the most part had become so expensive that they could not effectively compete against companies such as Glock and Smith & Wesson in the US market.

The company decided to begin with a clean slate and gather input from the shooters themselves to influence the design of the new pistol. H&K also decided that their next pistol should be developed primarily for the US market. Accordingly, H&K conducted a market survey to determine the preferences of American handgun shooters of all types, including military, law enforcement and civilian. This study was completed in July 1989.

The H&K study revealed a number of facts regarding the American handgun market which many firearms manufacturers would do well to heed. Perhaps most important was the fact that people who were serious about handguns were conservative. Whether they were professionals or simply serious enthusiasts, they preferred a handgun of conventional design. This is not to say that the American market is hostile to innovation – far from it. Americans have traditionally been enamored with innovation and technology, but technology alone cannot replace that which is of proven efficacy unless it improves upon it. Heckler & Koch concluded that a conventional pistol incorporating as many high-tech innovations as possible would be most attractive to the American market. Affordability was another major concern. While many people might well have purchased an innovative H&K P7, its high price made that pistol a non-starter for most individuals and law-enforcement agencies. Other major considerations were high quality, durability and reliability, safety, accuracy, magazine capacity and low recoil. And finally, the science of ergonomics would play a large part in design of the new pistol. After their market study, Heckler & Koch compiled and prioritized the characteristics of what would eventually become the Universal Self-loading Pistol, now simply known as the USP. In addition to the characteristics already noted, it was decided early in the design process that the pistol would be a double-action/single-action (DA/SA) with the capability for straightforward conversion to a number of different configurations to satisfy the requirements of as many users as possible. H&K also decided that the pistol would be initially chambered for the .40 S&W cartridge with other calibers to follow. This decision was based on the increasing popularity of the .40 S&W, which delivers ballistics nearly on a par with those of the venerable .45 ACP, although with less recoil. Also, a pistol designed from the outset for .40 S&W would have no problem accommodating the less powerful 9x19mm cartridge. H&K had noted that some .40 S&W pistols that were modified from 9x19mm designs had durability problems and they wanted to ensure that there were no such problems with their new pistol. In fact, the USP was the first pistol specifically designed for the .40 S&W cartridge. Design development began in September 1989 and took nearly two years. The head of the design team was Helmut Weldle, designer of the P7 pistols.

By May 1991, basic USP design work was nearly completed and the desired characteristics agreed upon. Shortly thereafter, in August, H&K began design work on the Offensive Handgun Weapons System (OHWS) for the United States Special Operations Command. This design was later type-classified as the Mark 23 Mod 0 USSOCOM Pistol, hereafter referred to as the Mark 23. While development of the Mark 23 pistol was concurrent with that of the USP and the final products shared many similar characteristics, they were developed independently within H&K.

The fact that the USP went into production after the Mark 23 prototypes were delivered to the US Government for testing is not indicative that the USP design was derived from the USSOCOM handgun. On the contrary, if anything, many of the Mark 23’s features were derived from the USP, which was already under development when the US Government’s request for proposal (RFP) for the OHWS was announced in December 1990. At the same time, development of the USP was influenced by the Mark 23’s development process. The development of the Mark 23 will be covered separately. While the Mark 23 is not a member of the immediate USP family, it is a first cousin and must be included in any discussion of the USP’s development.

By late 1991, the first prototype of the USP had been constructed and the USP name assigned to the new pistol. Two further prototypes were produced and tested during 1992. Testing was successful and the basic design was “frozen” in December of that year. Reliability testing on the USP prototypes was unfinished at the time of the design “freeze,” but since both pistols had fired 10,000 rounds of their 20,000 round reliability test without incident, it was decided to freeze the design and proceed with production planning and formal introduction of the USP at the January 1993 Shooting, Hunting and Outdoor Trades (SHOT) Show. Actual production of the USP40 was undertaken in February 1993.

At this point, it is worth noting the testing process that the USP underwent in the final stages of its development. The fact that the pistol passed a 20,000 round reliability test without meaningful wear on any component or any effect on accuracy has little meaning until one considers that the tried and true M1911A1 pistols which still serve in some military special operations units (not all have purchased the Mark 23 at the timeof this writing) require a depot-level rebuild after approximately 12,000 rounds to ensure accuracy and reliability. Another measure of the rugged design of the USP is the fact that unmodified USP45s have presently fired over 6,000 rounds of the new .45 super ammunition without incident. M1911-type pistols must be modified to reliably fire the .45 Super cartridge. Both USP45s and the Mark 23 are being tested with this new cartridge with a view towards certifying both pistols for its unlimited use. .45 Super testing should be complete by mid-1998 and results made pubic shortly thereafter.

USP testing was heavily influenced by the development of the Mark 23, which had to meet stringent military durability and reliability standards. The tests of the USP paralleled the NATO military test protocols of the Mark 23, which are much more stringent than commercial standards. The USP pistols were subjected to test firing in various attitudes and were checked every 1,000 rounds for damaged or broken parts and for accuracy. After each 10,000 rounds, the slide was manually cycled 1,000 times. A bullet was driven into the forcing cone of the USP barrel, a live round chambered and the pistol fired. There was no damage to the pistol and accuracy was unaffected. Another bullet was driven 30mm into the muzzle of the pistol and the pistol fired, again with no damage or degradation in performance. The pistols were dropped onto rubber on all sides and at a 45 degree angle onto the muzzle from a height of four feet with a primed case in the chamber, 13 dummy rounds in the magazine and the safety/decocking lever set in the “fire” position without incident. The pistols were then dropped six times onto a cocked hammer from a height of three and nearly seven feet onto a steel/concrete surface. There were no primer indentations in any of these tests. For ammunition compliance testing, USPs were tested using every type of commercially available ammunition.

Environmental testing of the USP was virtually identical to that of the Mark 23. The USP had to function in temperatures as low as -51O Fahrenheit and as high as +145O Fahrenheit. It functioned after a ten minute mud bath, after a ten minute exposure to blowing sand, freezing rain (water spray on the pistol to a thickness of 1 to 3mm). After these torture tests, the parts of four different pistols of different caliber were interchanged, except for barrel, slide and magazine. The USP passed or exceeded all tests and the .40 caliber pistols were placed on the market in the United States in April 1993. The 9mm USP followed in September.

The USP is, as we have stated, largely a traditional pistol design executed in nontraditional ways. It is a short recoil, modified Browning system similar to that used in the Browning M1935. This system is simple, very reliable, inexpensive to produce and makes barrel replacement easy. Unlike the system used in the M1935, the H&K locks on the front and rear edges of the ejection port, rather than using locking grooves machined into the slide and barrel.

The safety/decocking lever, called a “control lever” by H&K, is positioned at the same relative location on the frame as that in both the M1935 and M1911 pistols, and functions in the same fashion – up is “safe,” down is “fire.” There is one difference, however. Pressing the lever down past the “fire” position usually decocks the USP when the hammer is cocked. The lever then automatically returns to the “fire” position, enabling the USP to be operated in the double action mode for the first shot. This feature also allows the USP to be safely carried in “Condition One” – cocked and locked, which is favored by many armed professionals who are intimately familiar with the M1911 Colt Government Model and its many copies. Unlike the M1911, however, setting the USP to the “safe” position does not lock the slide. The control lever can easily be set up for left hand, right hand, or ambidextrous use. It should also be noted that besides having controls which are very similar in function to those of the M1911, the grip angle of the USP is identical to that of the venerable Browning design. Thus, an individual familiar with the M1911 or M1935 can pick up a USP and become familiar with it with very little familiarization training. Not all USPs, however, incorporate this system. The versatility of the USP allows it to be configured without a safety or decocking position in some versions. The different versions into which the USP can be configured are shown in Table 1.

Table 1: USP & Mark 23 Specifications

The slide release of the USP is also located similarly to that of the M1911 and M1935 and like the earlier designs is used to disassemble the pistol. The ambidextrous magazine release, however, is a real improvement over the traditional M1911 “push button.” The magazine release of the USP is located in essentially the same position as the older pistols, but instead of having to push in to release the magazine, the release button is pressed down to drop the magazine. To the author, at least, this is a much more natural movement than pressing in. The release is actually shielded by the trigger guard to prevent inadvertent actuation. We should also note that the magazines of the USP drop free when the release is pressed, an important tactical consideration. Despite this, there are “tearaway grooves” on the sides of the grip just in case….

The USP incorporates three or four separate safety mechanisms, depending on variant. Two of these safeties, the disconnector and the firing pin block, are passive. All USP pistols incorporate these two passive mechanisms. Six of the nine USP variants have a manual safety/decocker. Variant Seven has the double action safety with no manual control lever at all. Variants Three and Four do not have a manual safety, but have a decocking lever. The reader can determine the specific features of USP variants by referring to the chart accompanying this article. While Variant Eight is listed in the chart matrix, it was never produced except in very small numbers for US Immigration and Naturalization Border Patrol testing. Variant eight was essentially a Variant Seven USP with European tritium sights.

The barrel of the USP is cold hammer forged. Early pistols had six lands and grooves with a right hand twist. .40 S&W USPs were rifled with 1 turn in 14.96 inches, while 9mm Parabellum pistols had rifling at a rate of 1 turn in 9.84 inches. In November 1994 the rifling was changed from conventional lands and grooves to polygonal rifling, an H&K innovation. Twist rates remained the same as in earlier guns, but the cold hammer forged polygonal rifling has several benefits. Muzzle velocity is increased versus standard rifling due to a tighter gas seal. Because there are no sharp edges, bore wear and erosion are reduced, thus providing longer service life. Barrels with polygonal rifling are easier to clean and maintain because there are no grooves, per se, in which fouling and metal deposits can accumulate. Finally, polygonal rifling increases accuracy. The USP45 was never manufactured with conventional rifling.

The polymer frame of the USP continues a Heckler & Koch tradition that dates back to the mid-1960’s VP70, P9S and other H&K firearms. The precise makeup of the polymer frame is proprietary, but it is glass-fiber reinforced with metal guide rails on which the slide runs. As previously mentioned, the grip has “tear away” grooves to enable the shooter easy access to the magazine floorplate in case the magazine does not drop free when the release is pressed. The trigger guard is oversize to allow use of gloves and is shaped so as to help prevent the magazine release from being inadvertently pressed, which could prove highly embarrassing, not to mention fatal! The entire surface of the frame is textured for a positive grip, even with wet hands. The USP’s texturing is very similar to that of the Mark 23 and incorporates stippling on the grip side panels and deeply embossed grooves on the grip front and backstraps. A lanyard loop is molded into the heel of the grip as part of the insert that retains the hammer spring. The magazine well is beveled and stepped to facilitate reloading.

Another feature of the USP frame is the molded in grooves for mounting accessories such as laser, tactical lights, optical sights, or muzzle compensators. The grooves are parallel with the bore of the pistol, so any accessory mounted is boresighted when mounted. H&K claims that the grooves are more secure and resistant to recoil forces than trigger guard mounts in addition to providing automatic bore alignment for attached accessories.

H&K makes a full range of accessories for all versions of the USP, including a tactical light, designated the Universal Tactical Light (UTL), a UTL carrying pouch which allows the UTL to be attached to long guns, tools, bicycles, etc. H&K once manufactured the “Quik-Comp” muzzle brake/compensator which attached to the mounting grooves. This may still occasionally be found as a used component. Finally, H&K has an Optical Sight/Scope Mount available for the USP. This mount incorporates a Weaver mounting rail, can be used either with or without the “Quik-Comp,” and does not interfere with the pistol’s iron sights. The popularity of the USP has caused after-market manufacturers to begin producing similar accessories for the USP pistol family.

Magazines of the .40 S&W and 9x19mm pistols are of polymer with a stainless steel insert, while that of the USP45 is steel. Magazine capacity is 13 rounds in .40 S&W, 15 rounds in 9x19mm and 12 rounds in .45 ACP, except for civilian use pistols, which are all equipped with the silly federally-mandated “politically correct” ten-round magazines. The reader should be aware that there are no unmarked “pre-ban” .45 magazines for the USP. Any “pre-ban” magazines for the USP45 are in fact stolen Mark 23 magazines. Caveat emptor! The .45 caliber magazine was made from steel to keep grip circumference down while maximizing magazine capacity. The .45 magazine design is virtually identical to that of the Mark 23 USSOCOM Pistol. All magazines drop free when the release is pressed, contain “round count” holes with numbers and can be disassembled for cleaning and maintenance by the owner, even the “politically correct” ten-round civilian-use magazines.

A unique feature of the USP is its recoil reduction system, again virtually identical to that used on the Mark 23 USSOCOM Pistol. Essentially, the recoil reduction system consists of two concentric springs held in place by a guide rod. The outer recoil spring is a lower rate than the inner buffer spring, which slows the slide at the end of its recoil movement, prevents the slide from impinging against the frame of the pistol and buffers the unlocking of the barrel from the slide during the first three to four millimeters of movement. The buffer system reduces recoil forces by approximately 30 per cent and provides a number of benefits. First is reduced felt recoil to the shooter, resulting in reduced muzzle “flip” quicker recovery time after each shot and increased accuracy. Another benefit is reduced stress on components, which is one of the reasons for the extremely long service life of all USPs. The USP recoil reduction system is “transparent” to the shooter; it is insensitive to ammunition, requires no maintenance and has an indefinite service life. On early USPs, the recoil spring could be removed from the guide rod, but in September 1994, a “captured spring” design was incorporated, which makes USP disassembly and reassembly easier and safer. The new recoil reduction system can be retrofitted into earlier USPs without modification.

USP Compact pistols have a different recoil reduction system than the larger pistols because there is insufficient space for a dual-spring system and because the compact designs use a flat recoil spring to save space and facilitate shortening the barrel and frame. The buffer in the H&K USP Compacts is therefore a high strength polymer bushing that surrounds the recoil spring and cushions the blow of the slide against the frame as the slide recoils. Life of this polymer buffer is stated to be over 20,000 rounds.

The polymer frame of the USP is virtually impervious to wear or corrosion, but the USP, like all firearms, also incorporates metal components, which are subject to corrosion and wear unless protected. Heckler & Koch applies a proprietary Hostile Environment (HE) nitrogen/carbon finish to the USP slide. This finish is not only extremely hard (732 HV1 Vickers), but highly corrosion resistant, as well. The non-reflective HE finish has been used on the G3SG1 sniper rifle since the 1970’s and has proven itself in service. A stainless steel slide is available for all USP models. All other USP components, both external and internal, are finished with Dow-Corning’s “Molykote,” a very tough corrosion-resistant finish which also incorporates low-friction qualities.

Two versions of the USP which are not available in the United States are H&K’s German military P8 and P10 pistols. The P8 replaces the Walther P1 (modernized P.38) in Bundeswehr service, while the P10 is being issued to German police. Both are versions of the USP9 and USP9 Compact, respectively, but with two differences in comparison to other USP versions. Indeed, these pistols could be considered a new USP variant, were they commercially available. One difference is the functioning of the control lever, which reverses the “safe” and “fire” positions of the Variant 1 USP. The uppermost position of the lever on both German pistols is “fire,” rather than “safe.” The mid position is “safe,” and fully down decocks the pistol, as with other USP variants. The second difference is that when the trigger is released on the P8 and P10, the control lever automatically returns to the “safe” position. Some 20,000 USP “P8” variants have been issued to the German military.

Table 2: Mark 23 & USP45 Tactical Pistol Comparison

(Only items where specifications differ are listed)

*Fixed sights. Weight with adjustable sights is 32 ounces.
** Fixed sights. Height with adjustable sights is 5.78 inches.
*** Five shots, 25 meters, service ammunition.

The USP45 was a follow-on to the original USP40 and USP9 pistols and was introduced in January 1995 at the SHOT Show. The pistol became available for sale in May of that year. The change to .45 ACP caliber was not as simple as changing barrel, slide and recoil spring. As mentioned earlier, the USP45 steel magazine was essentially carried over from the Mark 23 USSOCOM Pistol because use of polymer magazines would have caused the grip circumference to be too large. The recoil reduction system was lengthened to accommodate the longer .45 ACP cartridge while providing an identical 30 per cent reduction in recoil forces. The USP45 was the first pistol to incorporate an improved trigger system which is not only smoother and lighter than the original, but also virtually eliminates “stacking,” or increased resistance as the trigger is pulled back in double action. In the USP45, the double action trigger take-up does not begin until the trigger reaches the “half-cock position. This enhanced trigger feature was incorporated into all USPs in early 1995. As stated, the USP45 is different than its smaller caliber sisters. While the USP9 and USP40 share virtually 100 per cent parts interchangability, only 78 per cent of USP45 parts will interchange with the earlier guns. The USP45 was subjected to and passed all the tests of the earlier firearms, including a durability test of 24,000 rounds of +P ammunition.

As we have seen, the USP pistols were designed with the American market in mind and the success of the pistol in the US market and overseas clearly indicates that Heckler & Koch was “on target” with its design. One of the major trends in the US firearms market has been engendered by the spread of “shall issue” concealed carry laws in the majority of the states. As of this writing in early 1998, 32 states have “shall issue” concealed laws which mandate that any citizen of good character who applies must be issued a license to carry a concealed weapon, usually a pistol. This has engendered a demand for compact pistols and many manufacturers have begun producing pistols designed for concealed carry. Compact versions of the USP for concealed carry were therefore virtually inevitable. .40 S&W and 9x19mm USP Compact pistols were introduced in early 1997 and a USP Compact .45 followed that autumn. Aside from the shorter length and height, there are minimal differences between the compact USPs and their full-size sisters, most of which have already been discussed. First, of course is the fact that the pistols are smaller both in height and in length for concealment. Grip circumference and trigger reach are also reduced for improved handling. Dimensional differences may be found in the specifications tables.

Unlike many “scaled down” pistols, the grips of the USP Compacts accommodate the entire hand of most shooters, even without using the extended floorplate magazine. (The USP Compact is shipped with two magazines – one with a flat, flush-fitting floor plate for maximum concealability and another with an extended floorplate to provide maximum comfort for those with large hands.) In terms of overall size, the USP Compacts are very close dimensionally to the Colt Officer’s ACP except for the slide, which is slightly thicker. Other changes in the compact pistols were the previously discussed recoil spring and buffer mechanism. The author had the opportunity to test one of the USP45 Compact pistols in October 1997 and shortly thereafter purchased one for personal use. It has since had several thousand rounds fired through it without a single stoppage.

The next iteration of USP is the USP45 Tactical Model, shown at the 1998 SHOT Show and officially put on sale in April, although the USP45 Tactical Model will not be available in quantity until May 1998. The Tactical Model USP is essentially a “cross” between the Mark 23 and the USP, incorporating the best features of both. The USP45 Tactical Model uses the barrel developed for the Mark 23, which is threaded for attachment of a suppressor. USP45 Tactical threads, however, are left handed to prevent installation of the Mark 23’s suppressor, which was designed for a heavier slide. At the time of this writing, a Knight’s Armament Company stainless suppressor and a Brugger & Thomet aluminum suppressor are available for the USP45 Tactical. The sights on the USP45 Tactical are fully adjustable and are designed to look above an installed suppressor. Trigger pull is greatly improved over earlier USPs and an adjustable trigger top is incorporated as a standard feature. Magazines are of an improved design with an extended floor plate to improve retention. All USP45 Tactical pistols are provided with a cleaning kit, spare barrel “O” rings, and tools for sight and trigger stop adjustment.

It is clear that the USP45 Tactical was designed for military and law enforcement use, but this requires some explanation. Several US military special operations forces did not purchase the Mark 23 and continue to use modified M1911A1 pistols, which are reaching the end of their service lives, despite having been rebuilt by military special operations armorers time after time. Moreover, while the M1911A1 will continue to function beyond 20,000 rounds, it begins to lose its accuracy after approximately 12,000 rounds and must be depot rebuilt. The failure of all special operations organizations to purchase the Mark 23 was not engendered by any specific fault of the Mark 23 itself; the pistol was built to the specifications determined by USSOCOM and surpassed all of them. In the words of one special operations requirements officer, “The Mark 23 isn’t a bad pistol; it simply doesn’t meet our requirements.” The fact is that USSOCOM does not directly speak for all special operations forces, nor can it require them to purchase a pistol that does not meet their individual service requirements. This will be further discussed in the section on the Mark 23 which follows. Nonetheless, a military requirement exists for a .45 caliber pistol that is different than the Mark 23, while improving on the venerable M1911A1 and at the same time maintaining the operational characteristics virtually identical to those of the Mark 23. Although Heckler & Koch has made no official comment regarding the intended market for the USP45 Tactical Pistol other than the statement, “…the Heckler & Koch USP45 Tactical Pistol is designed for users who require the features of the H&K MK 23/Mark 23 pistol for tactical, combat, or CQB use in a smaller and more affordable package.” (boldface in original), it is clear that the Tactical Pistol is aimed (no pun intended) at this market, and if the basic characteristics of the USP45 Tactical Pistol are any indication, it can be expected to be seen in the hands of many military and police special units in the coming years.

What does the future hold for the USP? The immediate future for the US market will see the USP product line expanded to include .357 SIG caliber. This addition to the USP product line will appear in the second half of 1998. In Germany, Heckler & Koch is entering into IPSC Competition and has developed a “full-race” version of the USP for use by its IPSC team. The IPSC pistol, called the “Expert Model” goes on sale in Europe in late June and if it achieves success in European IPSC circles, it may well be added to the American USP product line. The proven excellence of the USP design means not only that the pistol will be available for many years to come, but that the variety of USPs available to the shooter will continue to grow as well.