HK USP vs. Glock 17 Gen4 vs. XDM 4.5

HK USP vs. Glock 17 Gen4 vs. XDM 4.5

When worlds collide

By Dennis Adler

Unequal equals, the Umarex HK USP introduced late last year is a polymer frame pistol just like the Air Venturi Springfield Armory XDM 4.5 (left) and Umarex Glock 17 Gen4, but the centerfire gun that the HK USP is based upon is 30 years old. The Gen4 Glock was developed from the 1982 G17 but in 2010 was a completely revised design compared to the original Glock 17. The XDM centerfire model was introduced in 2008, so technically the HK USP is the oldest of the three designs and was as groundbreaking of a pistol back in 1989 as the original Glock 17 was in 1982. And as I have mentioned before, HK developed a pistol with a plastic (ABS) frame almost a decade before Glock’s polymer frame concept.

The only thing the Umarex Heckler & Koch USP has in common with the Umarex Glock 17 Gen4 and the Air Venturi Springfield Armory XDM 4.5, other than all three being blowback action CO2 pistols, is that the HK also uses a polymer frame. The centerfire guns share that in common as well, but the HK USP is far more traditional in its design, first, being a double action/single action pistol (DA/SA), secondly, being a hammer-fired design vs. two striker fired designs, and lastly, being a pistol that can be de-cocked and carried 100 percent safe with a chambered round and a manual safety set. In the real world of centerfire pistols these are features that law enforcement, military, and seasoned gun owners grew up around, and handguns that offered these features were the norm; guns like the Glock 17 were the exception. Those roles have reversed themselves today, and semi-autos like the Heckler & Koch USP, though still carried by some law enforcement agencies, and preferred by individuals who want “options” in how their handgun can be carried, is not what the majority of people are carrying. The HK is a graduate of the “Old School” only with a polymer frame that sets it apart from other DA/SA, hammer-fired contemporaries. The CO2 models of the HK, Glock and Springfield Armory pistols embody all of those differences and make it possible for air gun enthusiasts to make the same choices and weigh the advantages, disadvantages, and authenticity of each in much the same way.

What a sight…all three air pistols have white dot rear sights, well, the Glock is a white outline not dots, but white is still the framework for aiming the front sight. Here the advantage for some shooters goes to the red fiber optic used by Springfield Armory, but the rear view tells another story. While all three use polymer frames, the HK is a conventional hammer-fired pistol while the Glock (center) and XDM are striker-fired designs. Only the HK has the capability to be manually de-cocked, cocked and carried with a loaded chamber and the pistol put into a SAFE condition with a manual thumb safety.

Of course, all three air pistols can be had for a fraction of the cost of any single example of the centerfire guns, so some of you may already have all three in your collection. This article is for the rest of you who have one, none, or are still on the fence about getting a new blowback action pistol that really delivers on quality build, authenticity of design, realistic handling and BB pistol range accuracy. In my mind the HK USP was that gun for me last year (even though it did not win Reproduction Air Pistol of the Year), because I prefer older designs, the choice of DA/SA trigger pull, and the ability to manually cock and decock a pistol. In this trio of polymer frame examples only the HK meets those standards. But there is a little more to it as you dig deeper.

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The devil in the details

The Umarex HK USP is based on the standard version Heckler & Koch model V1 configuration, DA/SA with safety/decocking lever on the left side. For centerfire models there are 10 different variations of the USP each designed to meet the various needs of law enforcement, military and versions for either right or left-handed shooters. It is an extremely well thought out platform. Unlike the Springfield XDM and Glock 17 Gen4 which were improvements over earlier designs, the USP was designed by a new engineering team at Heckler & Koch (established in 1989) to create a pistol for consideration by the U.S. Army under the SOCOM project (United States Special Operation Command). To rationalize developmental costs the new semi-auto had to be suitable to both military, law enforcement and civilian markets, and thus the USP “Universal Self-Loading Pistol” was introduced to the civilian market in 1993, and has been in continual production for over a quarter of a century. It may have been new in 2018 as a blowback action CO2 model, but the USP design is by no means a “new” gun.

The HK was designed in an era of one-size fits all like the original Glock 17. The grip size and contour of the HK is of medium size with an angle that is very close to a Colt Model 1911. The newer Gen4 Glock and Springfield Armory XDM offer three interchangeable backstrap sizes to better accommodate a wider number of end users. The CO2 models have the same features. The advantage the HK has is being a DA/SA pistol that gives the user greater handling latitude. The USP also has a larger triggerguard with a deep undercut.

The USP is based on features that were expected by shooters who had been raised on legendary models like the Colt 1911, Browning Hi-Power, and S&W Model 39 (America’s first DA/SA semi-auto). So, this is, as I said an “Old School” handgun, only it has a polymer frame.

The HK USP CO2 model is an accurate reproduction that utilizes a short-recoil, locked-breech, tilting-barrel design like the centerfire pistol. What that means is that the barrel lug (top rear portion of the barrel assembly that is exposed in the slide ejection port) interlocks with the slide when the gun is in battery. When fired, it unlocks and tilts down, and the front of the barrel tilts up.

Operating systems for all three CO2 models are based on their centerfire counterparts, which use a short-recoil, locked-breech, tilting-barrel design. As can be seen here with the slides pulled back just slightly, the top of the barrel lug has disengaged from the slide ejection port and is beginning to tilt down allowing the slide to move back. The HK USP and XDM 4.5 have a more pronounced tilt than the Glock.

At this point the slide and barrel have disengaged as the slide continues its rearward motion to eject the spent shell (in the centerfire gun) and re-cock the hammer as the slide reaches it furthest rearward motion. It is then pulled closed by the decompression of the recoil spring. As the slide travels forward it strips a new round from the magazine and chambers it (or with the CO2 model chambers the next BB in the magazine) and closes. During the closing motion, the barrel tilts back down, the lug tilts up and locks back into battery with the slide making the gun ready to fire again. The HK and Springfield XDM models do this exactly the same as their centerfire counterparts. The Umarex Glock 17 Gen4 abbreviates this by having a barrel lug that fits snugly into the slide but only disengages enough to allow the slide to move back, and the barrel does not noticeably tilt up. This is shown in the photo of all three guns with their slides locked open.

With the slides locked open you can see the tilting-barrel (front of barrel tilts up as rear barrel lug tilts down) on the XDM (right) and USP. These two CO2 models operate just like the centerfire pistols. The Umarex Glock 17 barrel, however, does not tilt up like its 9mm counterpart. There is only a very slight change in the angle of the barrel when the Glock CO2 model fires or the slide locks open.

All three fieldstrip exactly like their centerfire counterparts and again authenticity plays a role in exacting detail. To fieldstrip the USP the slide release has to be removed (Old School) while the Glock has dual release catches (one on either side) that have to be pulled down simultaneously allowing the slide to be pulled forward off the frame, and the XDM has a disassembly lever that has to be rotated up allowing the slide to be pulled forward off the frame. Both the Glock and Springfield models have eliminated the need to remove a part from the gun to perform a basic fieldstrip, while the HK still uses the same fundamental slide release as a Colt Model 1911 to anchor everything together. This is no more or less complicated but it does make the gun vulnerable to being left unserviceable if the slide release is lost. This can’t happen with the Glock or XDM.

Field stripping has been the make or break feature for several blowback action CO2 models and the HK USP is an excellent example of an air pistol that utilizes as much of the centerfire design as possible to make it authentic. Unlike the XDM and Glock 17 Gen4 designs, the slide release has to be removed to fieldstrip the pistol. This is a more traditional design.

As for authentic feel, the Glock comes as close as possible to the centerfire model in terms of slide resistance, but so does the HK USP which also has a heavy dual recoil spring design making the effort to rack the slide feel closer to a centerfire gun.

With the Glock you pull down the two disassembly releases (one on either side of the frame) simultaneously and then pull the slide forward off the frame, remove the recoil spring, guide rod, and then the barrel.
The same thing is done to fieldstrip the XDM, only instead of two takedown releases, the Springfield Armory pistol uses a more conventional takedown lever that is rotated up to allow removing the slide from the frame.

The biggest advantage in the HK design as a CO2 model is the actual use of a decocker and manual safety combined with a fully functional double action/single action trigger and external hammer that can be manually cocked to fire the first round (and thus sidestep firing the first shot double action). This does away with the need for an extra manual safety which, however cleverly disguised on the Glock and Springfield CO2 models, is a non-authentic feature. As a safety against accidentally discharging the gun, since the safety is incorporated into the trigger on the Glock, it is a good feature for an air pistol. The XDM also has the grip safety, which would make it impossible to accidentally pull the trigger and discharge the gun without a firm grasp on the grip. Still, there is something to be said for having that thumb safety right there to click off when you are ready to shoot, and the knowledge that if you don’t shoot, the gun can be safely de-cocked and re-holstered. Old School thinking.

The Umarex HK USP was introduced in 2018 but the gun is a 30 year old design that was on the cutting edge in 1989. The USP is still in production and sees use the world over. Its old school hammer-fired design, and use of a safety and decocker make it a very straightforward pistol to handle, and one of the safest to carry. As a CO2 model it is almost in a class by itself with a DA/SA trigger system and polymer frame. It is also the lowest priced of the three CO2 models, selling for $99.99. The Glock Gen4 sells for $129.95 and XDM for $119.99.

Velocity and accuracy

We know from the recent series of articles I have done on the Gen4 and XDM that both guns shoot at about the same velocity and can produce tight groups at 21 feet. Looking back at my tests of the Umarex HK USP, average velocity for that gun using Umarex Precision steel BBs was 328 fps, with a high of 333 fps, a low of 323 fps and a standard deviation of 3 fps for 10 shots. Factory rated velocity for the USP is 325 fps. Compared to the XDM and Gen4, with an average of 310 fps, a high of 313 fps and a low of 307 fps for the Glock, and an average of 307 fps, high of 313 fps, and a low of 300 fps for the XDM, there is a slight velocity advantage for the HK over the newer CO2 models.

Downrange at 21 feet, the HK delivered a best 10-shot group using Umarex steel BBs of 1.375 inches (shot in two 5-shot groups) with the best 5-shots at 0.56 inches in the bullseye. This falls right in step with results obtained shooting the Glock Gen4 and Springfield Armory XDM 4.5 with Shoot-N-C targets. The HK USP, then, is a third equal among equals. So what makes the difference?

With a slight velocity edge of 328 fps, the USP can keep its groups as tight as the XDM and Gen4 at 21 feet. Best 5-shot group measures 0.56 inches.


The difference in velocity and accuracy between these three pistols is negligible, a better shot could improve on my results, shooting from a benchrest, as some of you prefer, would likely render even better accuracy, so why would you pick one over the other. All three use the same type of self-contained CO2 BB magazines, have excellent sights (albeit fixed sights, while their centerfire counterparts have drift adjustable rear sights and can be equipped with better tritium night sights or target sights), and all three have very good triggers and light average trigger pulls in the 5 to 6-pound range. What separates these guns is time. When the HK was developed hammer-fired guns were preferable, de-cockers were desirable, as was a manual or ambidextrous thumb safety. Between 1989, when the HK USP was developed, and 2008 and 2010, when the XDM and Glock Gen4 were introduced, a lot has changed in the world. And it keeps changing. Back in 1989 my taste in contemporary handguns still leaned toward S&W revolvers, the only modern semi-autos I owned were Walthers and Colt (or Colt-based) 1911s. My taste in everyday handguns hasn’t changed that much in 30 years, but CO2 models like the HK USP, Springfield Armory XDM and Glock 17 Gen4 have given me a chance to revisit some of those decisions. And while I still favor older styles, and thus my personal preference for the HK CO2 model, modern designs like the XDM and Glock Gen4 so well represent their centerfire counterparts that they allow you to consider their advantages over older and more traditional handgun designs. The airgun experience lets you do just that.

A word about safety

Blowback action airguns provide the look, feel and operation of their cartridge-firing counterparts and this is one reason why they have become so popular. Airguns in general all look like guns, blowback action models more so, and it is important to remember that the vast majority of people can’t tell an airgun from a cartridge gun. Never brandish an airgun in public. Always, and I can never stress this enough, always treat an airgun as you would a cartridge gun. The same manual of operation and safety should always apply.

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