New HK UMP 45

At Last, Polymer Perfection in a .45 ACP SMG!
By Stephen Gearinger

More than a few professional submachine gunners have said that if the MP5 were available in a decent caliber, meaning .45 ACP, it would be perfect. Others observe that the MP5 is incomplete without a bolt hold-open device. Procurement types would like the purchase price of the MP5 and accessories to be cheaper by 30% or more. While those carrying .45 ACP pistols have settled for the MP5 in calibers 9mm, 10mm or .40 S&W, they would still have preferred one in the same caliber as their .45 handguns.

Heckler & Koch has demonstrated it's not a company that rests on its laurels, basking in the glory of its current product. Time and again over its 50 years of existence HK has pushed the envelope of small arms design and performance. HK has pioneered evolutionary if not revolutionary developments such as the first production polymer-framed pistol, the VP70, in the early 1970s. The world's first caseless ammunition rifle, the G11, which elicited the statement from the U.S. Military that this unique weapon firing self-consuming 4.92mm rounds proved the feasibility of caseless ammunition. The HK Close Assault Weapon System (CAWS), the world's deadliest shotgun and the latest development from HK, the OICW, the futuristic replacement to the US M203 in 2005, are "bullet launchers" pushed to the limits of technology and materials.

While many informed small arms enthusiasts have heard of these HK weapons, there was an entire family of HK submachine guns developed almost twenty years after the first MP5 was assembled as a prototype in 1965. These prototype sub-guns eventually brought along the genesis of HK's latest submachine gun, the new UMP45.

In the early 1980s, the U.S. Joint Service Small Arms Program (JSSAP) office solicited for an Advanced 9mm Submachine Gun to arm both conventional and special operations personnel. Calling for advanced features and design, the "JSSAP Gun" never advanced beyond prototype development with the exception of 60 that were reportedly hand-made expressly for, and issued to, one American unit that will herein remain nameless. HK developed numerous models and submitted them for exhaustive testing. In the end this customer decided to procure the off-the-shelf MP5 and the new HK's were relegated to their place in only the more exclusive history books.

The HK54A1 with its 50-round drum magazine and the subsequent SMG and SMG II prototypes were advanced 9mm SMGs built by HK during the 1980s for this military R&D program. The military's decision not to purchase the new HK SMG did not deter HK's drive to improve on the near perfection of the MP5. Throughout the late 1980s and early 1990s HK continued work on the concept of a modular submachine gun from which various configurations could be assembled by the operator for the specific mission. The use of advanced polymer materials found their way not only into the magazine but also into the receiver and many non-stress-bearing parts of the weapon. Prototypes of the MP2000 and the MP5-PIP (Product ImProved) were made and tested and have lead to the series production weapon HK now calls the "Universal Machine Pistol" (UMP).

Available by mid-1999 the UMP45, chambered for the ever-popular .45 ACP round, is truly the culmination of HK's decades of worldwide experience with the MP5 and the prototype weapons described above. Not able to properly "stuff" the short stubby .45 ACP round into the 9mm MP5's envelope, a new dedicated model was called for and design work began on the UMP45 in 1996.

A quick inspection of the new UMP45 shows that once again HK has done its homework well. This "polymer MP5" has all of the capabilities and features of the MP5 and more, yet none of its drawbacks. It is obvious to this writer that a great deal of end-user input has been incorporated into the weapon's design.

To say that the design and construction of the UMP45 is a departure for HK would be accurate. The years of HK stamping, folding and welding sheet metal to produce new weapon designs seems to have ended. The unique roller-locked bolt system also seems to be a thing of the past. Both the excellent HK G36 rifle and the new UMP45 employ polymers in the receiver and many internal parts. Metal inserts provide the strength and durability needed in the pressure bearing components and provide the guiding surfaces for the bolt. HK claims the UMP45 has a minimum service life of 100,000 rounds.

How It Works

The UMP45 operates off the simple blowback system, with a relatively lightweight bolt with few moving parts (extractor, firing pin, and firing pin block). The UMP fires from the closed-bolt position and features a fixed barrel, which is removable by the unit armorer. A bolt hold-open device, or bolt catch as it is often termed, is standard on the UMP45 and can be easily disabled. Fully ambidextrous operating controls including easily reachable safety/selector levers are present. Sounds good, you say? Well, it gets better. All these features are definite improvements over the MP5, as is the suggested law enforcement price of under $900. Yes, that's right, $900 U.S. dollars for an HK SMG, hundreds less than a comparably-equipped MP5.

The "U" in UMP stands for "Universal", which denotes the UMP's caliber-convertible capability, though at this time only a .45 ACP UMP is available. By offering the UMP first in .45 ACP, HK now has a fourth sub-gun caliber, one that will be welcomed by those carrying .45 ACP handguns. The UMP45 will easily handle a steady diet of ball, hollow-point and +P ammunition as well as limited amounts of the .45 Super.

To create the UMP, HK designers changed what needed changing on the MP5 and left the good things be. They correctly and intentionally left the operating controls of the UMP in the same position as on other HK weapons. Thus, someone already comfortable with the controls of their trusty MP5, G3, HK53, or even the new G36, will find the controls of the UMP45 right where they should be. New shooters will find the operating controls of the UMP to be user-friendly, well-placed and easy to actuate.

As with all HKs, the strong (firing) hand remains in place on the UMP45's pistol grip, while the free, weak (non-firing) hand actuates the operating controls. The cocking lever, magazine release lever and bolt catch can be easily actuated with the weapon still at the shoulder and ready for immediate use. The UMP45's safety/selector levers are ambidextrous but have been redesigned so even short fingers can rotate the safety/selector lever into the firing modes without the need to rotate the grip of the strong hand.

The bolt catch resembles and functions like that of the M16 or M4 and is actuated by the follower of the empty magazine. A quick jab of the thumb during magazine insertion closes the bolt and "primes" the chamber with a live round. Simple and efficient, it wastes no movement.

The UMP45 is delivered with fixed iron sights and molded-in attachment points for mounting rails (MIL-STD-1913 "Picatinny" rails) or other accessory devices. The rear sight is of a flip-up design with both open "V" shaped and peep apertures to allow for low-light acquisition and precision accuracy at smaller or long-range targets. A metric Allen wrench is provided for both windage and elevation adjustment, both made in the rear sight assembly. The front sight is a hooded post similar in design to that found on most HK long guns. Optional tritium sights will also be available for the UMP by the time it is fielded in mid-1999.

The rail mounting points are molded into the polymer receiver of the UMP45 at four separate points. These rails can be attached with the same Allen wrench used for sight adjustment. One six-inch section can be located on the top of the receiver in front of the rear sight. A second shorter four-inch section can be mounted at the left, bottom or right sides of the integral forearm of the weapon. Any device that fits on M16A3 and M4A1 variants can be attached to these UMP45 rails, to include light and sight mounts, vertical foregrips, QD sling aftachments, etc. A UMP45 rail will also be available for the HK MKII Universal Tactical Light (UTL).

The UMP barrel also incorporates a unique quick-detachable mounting system for muzzle-mounted accessories such as sound suppressors and flash hiders. Bothersome threads are unnecessary on this new system. A simple depresion of a knurled locking lever allows the sound suppressor to be mounted. Removal is just as quick and easy. No collars, springs or locking sleeves are required, nor do you need to push, rotate or pull the sound suppressor during mounting or removal. Proven during extensive testing, the repeatability and accuracy of the weapon when suppressed is assured by this innovative attachment method. This is going to be without question the hot ticket for QD suppressor attachment.

Lightweight, baffle-style aluminum Bruegger & Thomet (B&T) sound suppressors are being imported from Switzerland for sale with the UMP45. Sound reduction with ball ammunition is reported to be 20 dBA or greater. No visible muzzle flash was apparent during our limited testing.

As with most HKs, the 7.9-inch barrel is cold hammer forged. The UMP bore is chrome lined for durability and has HK's trade-mark polygonal rifling with a twist rate twist of 1 turn in 16 inches.

As with HK's G36, the UMP45 features a folding stock that pivots to the right side of the receiver. It is held in the folded position by a molded locking feature on the receiver, which doubles as a brass deflector. A rubber buttplate and cheekrest on the buttstock are also included.

The UMP disassembles into two halves that are held together by a hinge and a single locking pin, which stores in the buttstock during field stripping. The upper receiver contains the barrel, sights, cocking lever and folding buftstock. The lower receiver includes the magazine well, magazine catch, bolt catch, trigger mechanism, safety/selector lever and pistol grip. The bolt allows for the removal of the firing pin and spring and recoil spring assembly, without tools. A clever firing pin block, actuated by the strike of the hammer, insures that the firing pin remains locked unless the trigger is pulled, thus preventing slam fires or drop-induced discharges.

As the UMP45 is a simple, blowback-operated weapon, there is no need for the chamber fluting of the MP5. The brass ejection pattern is a consistent down and forward direction from the right side of the polymer receiver. The simplicity of the design makes for easy clean up after firing. No special tools or brushes are required and access to all of the critical areas for cleaning are enhanced by the upper/lower receiver design of the UMP. The polymer can tolerate any cleaning solvents safe for hands, and little or no lubrication is required.

Torture Test

During its development, the UMP passed all of the normal grueling military-style testing for which HK has become famous. Nearly every type of U.S. and foreign military and commercial ammunition has been fired over more than two years, and in quantities that would make your reloading machine wince. During our firing session more than 1,000 rounds were fired without a single stoppage, and this included ball, hollow-point, flat point, subsonic and even +P ammunition mixed randomly in the magazine.

The first thing that one notices when handling the new UMP45 is its light weight. The operating controls are familiar and, as we've noted above, like those of the MP5. The flared magazine well insures quick magazine changes. The polymer 25-round magazine features a clear plastic strip at the side for counting the rounds inside. A shorter magazine of ten-round capacity is also planned.

Filling the magazine by hand was easy. Magazine loaders are also available for extended range firing sessions. Lessons learned with the M3 Grease Gun didn't escape HK with the UMP45 magazine. A single feed position reminiscent of the M3 is apparent. Sling attachment points are provided for both left and right handed shooters.

Shooting any new weapon is always the final word in any evaluation. Many guns feel great in the hand and look good on paper but perform poorly where it really counts. The UMP45 did not disappoint us in this regard. The shooting went 100% flawless. We have to admit that the UMP is no beauty. However, form follows function, and this gun worked and handled wonderfully. The lightness of the weapon makes for fast aiming and target acquisition mandatory during the classic CQB role of a submachine gun. The UMP45 is quick when acquiring multiple or moving targets as well as while firing on the move.

The recoil impulse to the shooter's shoulder was no more than a 9mm MP5. With far more muzzle energy than a 9mm submachine gun, the UMP45 delivers superior ballistics compared to weapons in other calibers, except maybe the 10mm MP5. This is especially so when firing subsonic ammunition in a sound suppressed mode, a scenario where 9mm sub-guns have often faired poorly.

Compared to the MP5

For comparison purposes we were able to bring together MP5s in all three available calibers to test alongside the .45 caliber Universal Machine Pistol. We tested the four weapons for accuracy and controllability in both burst and fully automatic modes of fire including the tell-all, 25-round "Hell Mary" burst. Semi-automatic accuracy of the UMP45 was excellent - comparable to that of the MP5 in all calibers. Firing at 100 yards, the UMP45 placed all rounds within a 6-inch group on par with the 9mm, .40 S&W and 10mm MP5s. The hold at 50 yards was dead on and knothole-sized groups at 15 and 25 yards in semi-automatic mode were easy, both with and without the sound suppressor mounted.

For speed we employed the talents of a very experienced competitive shooter from our nation's leading law enforcement tactical team. Our drill involved shooting two 2-shot bursts on a single one-third-size steel silhouette from 15 yards. Firing from an unsupported shoulder position, the PACT timer recorded the results. Time and again this shooter completed this drill in less than one second from the ready position, both with his issue MP5 and the UMP45 firing 230-grain ball. Admittedly unfamiliar with the new UMP45, within minutes and with little practice his first rounds were on target in 0.70 of a second! We were impressed, and so was he.

Simple blowback, no locking rollers, light weight. None of this seemed to matter with the UMP45. Hits in the 2-shot burst mode were within 2-4 inches of the point of aim at 15 yards. This should be great news for tactical teams around the U.S. and especially those looking for improved terminal performance from their submachine gun in the sound suppressed mode. This gun would also make an outstanding squad car carbine with the semi-automatic only or semi-automatic and 2-shot burst trigger mechanism.

HK has done it again! They have created the first and only true modern production .45 caliber submachine gun that competes head to head with the abilities of the famous 9mm MP5. In doing so, they made sure that it was better, lighter, less expensive, more user friendly and far less complicated than the proven MP5. Best of all the UMP45 is available at a price where an agency could nearly buy two UMPs for the price of an MP5/10 or MP5/40.

first published in the April 1999 edition of Guns and Weapons for Law Enforcement

UMP45 Specifications
Caliber .45 ACP
Ammunition Feed Staggered magazines;
25-round capacity
Cyclic rate Approx. 580 RPM with ball ammo
Approx. 700 RPM with +P ammo
Sight Radius 12.80 inches
Weight: with empty
5.01 pounds
Barrel length 7.87 inches
Overall length 17.71 inches with stock folded
27.17 inches with stock extended
Width 2.50 inches
Height 12.76 inches with 25-rd mag inserted