The HK P9S Roller-Locked Handgun

By Will Dabbs, MD

What do the SIG P226, Glock, HK USP, Colt 1911, FN Hi-Power, Tokarev TT33, Walther P99, and CZ75 all have in common? Despite the fact that these guns originated from the four corners of the globe, the common theme to them all is the luminary John Moses Browning. In the history of mankind, John Browning is the undisputed master of firearms design. Kalashnikov made more guns. Stoner revolutionized the ergonomics and materials. Maxim likely claimed more lives. Browning, however, changed the very landscape. In the case of handgun design, the Browning operating system wherein the barrel tilted out of battery by means of a wedge or link still drives most of the world’s tactical handguns nearly a century after the man died.

There have been some interesting alternatives. The Walther P38 and the Beretta 92 employ a novel tilting wedge. A few designs to include the Beretta PX4 and the new Chinese CF98 use a rotating barrel with a cam system to lock the breech. Some designs just made the slide and recoil spring beefy enough to manage recoil energy and left it at that. Those brilliant German engineers at HK, however, once tried something completely different.

Big Bore Beginnings

A team of German engineers working for the firm of Johannus Grossfuss Metal-und locierwaffenfabrik in Doblen, Saxony, began work designing a replacement for the belt-fed MG34 General Purpose Machine Gun in 1939. The guys who designed the resulting German MG42 had never before designed a firearm. Given the requirements for a quick-change barrel and accelerated rate of fire perhaps this explains the unconventional nature of the gun. The MG42 was mostly steel stampings welded together and could be built en masse using modern production facilities without requiring excessive numbers of skilled machinists. The MG42 was portable, reliable, devastating downrange, and relatively cheap. The WWII-era design was so effective that it is still general issue in many armies even today. The beating heart of the MG42 was the delayed roller locking mechanism.

In the MG42, locking was undertaken via a pair of steel rollers that cammed out into corresponding recesses in the breech of the gun. This system made for a very smooth action that ended up being reliable in the face of fouling and high round counts. While there was some detailed machining required to produce both the bolt and barrel extension, compared to the MG34 that preceded it the MG42 was a breeze to build in quantity. The original roller locking system was actually inspired by the design of the industrial pile drivers of the day.

German engineers were so enamored with the concept that towards the end of the war they were adapting this system to drive a shoulder-fired assault rifle. After the armistice these engineers made their way to Spain and built their rifle as the Spanish CETME.

The CETME was chambered for 7.62x51mm cartridges and fed from a 20-round box magazine. Soon after its introduction the gun’s German designers went back to Germany and started production of a product-improved version for Heckler and Koch called the G3. Several calibers and countless variations later, this roller-locked operating system drove the HK33 and MP5 families as well. Never satisfied with creative stagnation, HK engineers eventually miniaturized the classic roller-locked operating system into the revolutionary HK P9S tactical handgun.

Vital Statistics

The 9mm P9S arose before the world’s fetish for high-capacity magazines so it feeds from a single-stack box magazine that holds nine rounds. The magazine release is on the heel of the butt in the European fashion and there is a simple slide-mounted safety. These are about the only aspects of the gun that aspire to normal, however.

There is a manual decocker on the left side of the frame that is accessible with the right thumb. Unlike the SIG-series guns, to render the weapon inert you depress the decocker, pull the trigger, and then lower the internal striker into a neutral position. Pressing the decocking lever all the way down also drops the slide on a fresh magazine.

The trigger on the P9S is simply outstanding and the slide is coated with something that feels a bit like Teflon. The P9S employed a polymer frame back when polymer frames weren’t cool. In this case the polymer portion is little more than a sheath that wraps around a metallic endoskeleton. After several decades of hard use the polymer frame on my example has had to be replaced twice.

The HK P9S employs such innovative features as polygonal rifling and a small mechanical indicator that protrudes from the rear of the slide when the action is cocked. As with all things HK, the P9S looks like a sewing machine on the inside but is executed to an incomparable standard of quality.

Turning Ammo into Noise

HK produced the P9S in limited numbers chambered in .45 ACP as well. However, most examples encountered today are in 9mm. Given the modest recoil impulse of this cartridge, the P9S is a very nice-shooting handgun. As is the case with its larger cousins, the MP5 and G3, the roller-locked action is almost unnaturally smooth. Follow up shots are easy and the heel-mounted magazine release is fairly intuitive if not quite as awesome as that of John Moses’ 1911.

My P9S is monotonously reliable despite years of use and is just the right size to tame the 9mm into a pussycat. Sights are decent and the barrel is stainless. Even after a bazillion rounds the P9S still groups competitively with any of my more modern iron.

One aspect of the novel roller-locked design that did find a passionate niche following was as a suppressor host. The roller-locked mechanism lent itself to a fixed barrel. That meant that a suppressor might be mounted without adversely affecting reliability or requiring a Linear Inertial Decoupler or LID device. This fact alone has guaranteed the popularity of the P9S years after it was discontinued from production.

There are frequently multiple right ways to reach a common destination. In the case of tactical handgun design there is basically John Moses Browning and then there is everybody else. Within that tiny subset of everybody else, HK engineers once conjured up a truly innovative way to skin the cat. You just cannot help but be impressed with how well the Germans pulled it off.

This article first appeared in Small Arms Review V19N6 (July 2015)
and was posted online on May 22, 2015


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