Short & Sweet: The Iconic MP5K

We pay tribute to one of the most popular compact submachine guns of all time, the versatile MP5K.

The year is 1964 — the same year the Colt M16 officially entered U.S. military service. In West Germany, engineers at Heckler & Koch have begun developing a new submachine gun based on the architecture of the H&K G3 battle rifle, which had become the Bundeswehr’s standard-issue weapon in 1959. The new SMG uses the same roller-delayed blowback architecture as the G3 (and the G3’s predecessor, the CETME). However, instead of coping with the stout recoil of a 7.62x51mm NATO rifle round, this operating system would be set up for the 9mm Luger pistol caliber. The resulting SMG was designated the MP64 after its first year of development, but later renamed the MP5.

Over subsequent decades, the MP5 would rise to prominence as the world’s most widely used submachine gun. It was adopted by military organizations in more than 40 countries, as well as a nearly endless list of law enforcement and private security entities. By the time the ’90s arrived, it seemed like everyone was using it — from British SAS to American Navy SEALs — and this is reflected in its countless pop culture depictions in movies, TV shows, and video games. The popularity also spawned more than 100 variants of the MP5 platform, including dozens of third-party clones. Some — such as those made in Greece, Iran, Pakistan, Turkey, Sudan, Mexico, and the UK — were manufactured with H&K’s blessing under license, while others were unofficially reverse-engineered (for example, China’s Norinco NR08).

Above: Paired with an MFI ultra-low-profile claw mount from HKParts, the B&T skeletonized riser on our Aimpoint ACRO red dot allows unobstructed use of the factory iron sights.

K is for Kurz

In 1976, the security detail for an unnamed South American head of state reportedly reached out to H&K to request a special variant of the MP5. They wanted a weapon that was small enough to conceal under a coat, but which was still ergonomic enough to be fired in controlled full-auto bursts. The resulting weapon was designated the MP5K, which stood for kurz — the German word for “short.”

The MP5K is characterized by its replacement of the MP5’s fixed stock with a flat buttplate and sling swivel, as well as a shortened 4.5-inch barrel up front. The K also had a shorter receiver and bolt carrier to reduce the weapon’s length as much as possible. In order to keep recoil manageable, a unique vertical foregrip was added. This grip includes a protrusion at the front to reduce the risk of the shooter’s fingers slipping forward past the muzzle. (Fun fact: The very first MP5K had a prototype grip made out of wood with a full-length knuckle guard that resembled a staple gun.) With its tiny size, lack of buttstock, and rate of fire of 900 rounds per minute, it’s a weapon that demands respect from the shooter.

Above: B&T’s telescopic stock has a one-way ratcheting mechanism with six possible positions. Simply pull to extend the stock; to collapse it, press the release button on the receiver buttplate.

Later versions of the MP5K added a longer tri-lug barrel that allowed users to mount a quick-detach suppressor, as well as an optional side-folding stock. There was even a special MP5K Operational Briefcase released in 1978, which completely concealed the weapon inside an ordinary-looking briefcase and allowed the user to fire it by pressing a trigger built into the carry handle. (See it in action here.)

Clone Wars

Remember the note about MP5 clones? Well, the weapon seen here is one such clone manufactured in Turkey by MKE and imported to the United States by Century Arms. It’s called the AP5-P, which is apparently short for “Apparatus Pistol” — a pretty silly name, but also a clear attempt to harken back to its origin without infringing on any trademarks. Century Arms’ product description makes the connection clear by stating that the AP5-P is “based and built off of the original and historic design from the 1970s.”

MKE, short for Mechanical and Chemical Industry Corporation, is a company that produces weapons for the Turkish military. Since the 1950s, they’ve made everything from aircraft and artillery systems to sniper rifles and belt-fed machine guns. But MKE’s MP5 clones aren’t just imitations; they’re made with original German tooling that was given to MKE under a license from H&K themselves. That license, under which MKE was fully trained and equipped by H&K to produce MP5s for use by the Turkish government, is long expired. However, when that license ended, MKE retained the manufacturing equipment and training that’s still in use today.

Our sister publication RECOIL toured the MKE facility in 2015 and saw some of this tooling firsthand, complete with a 1974 H&K data plate riveted onto it. Granted, the manufacturing of these guns may differ from H&K’s current tooling specs and procedures, but the original DNA is undoubtedly present. Additionally, as you’ll read about momentarily, the AP5-P is compatible with standard parts and accessories made for H&K MP5s and semi-auto SP5s.

Century Arms currently imports two other versions of this weapon, the AP5-M and regular AP5. The former mimics the original MP5K with a 4.5-inch flush-cut barrel; the latter matches the proportions of a standard MP5, only with a buttplate at the back of the receiver. If you decide to convert one of these guns from a pistol to a short-barreled rifle, adding a stock is as simple as popping out one or two pins at the back of the receiver and replacing the buttplate. For K-style variants, adding a vertical foregrip is equally simple.

First Impressions

When I picked up this AP5-P, I immediately took it out to the range for a quick break-in. After inserting one of the two included 30-round metal mags and slapping the charging handle — an action that still puts a smile on my face every time — I went to work on some steel plates at 25 yards. Anyone who has shot a roller-delayed blowback gun side-by-side with a direct blowback 9mm AR can attest how much smoother the recoil impulse feels, and the AP5-P was no exception. It shoots well, although the standard trigger is what you’d expect from a submachine gun designed in the ’70s (i.e., vague and heavy). The adjustable iron sights work great, and Century Arms includes a claw-style Picatinny optic mount to allow installation of your favorite red-dot sight.

Above: The front sight post light mount from Gibbous Outfitters serves as a low-profile, sturdy attachment platform for a Scout-style light body and tape switch.

Shooting an MP5K without the vertical grip feels odd, but thanks to the ATF’s unconstitutional regulations, I couldn’t legally add one until I paid for a $200 tax stamp and waited for an approved NFA Form 1. The same is true for adding a stock, but at least stockless is the MP5K’s natural condition. For the best shooting experience, I attached both hooks on the included MKE sling to the swivel on the buttplate and pressed the gun out, using sling tension against my body to stabilize it. This technique had me ringing steel with each trigger press in no time.

Foregrip & Stock

The first order of business was to return this AP5-P to its classic form by adding a vertical grip, and that meant registering it as a short-barreled rifle. Once the gun was an SBR, I reached out to a company that would become extremely helpful with the rest of this build: HKParts. As the name implies, they offer just about every part you could possibly need or want for any MP5 variant, including original German H&K components and clone parts that are made in the USA. I selected an HKParts-branded K vertical foregrip (HKP-20957) for my AP5-P, which was easily installed in place of the original MKE handguard. This version even has built-in M-LOK slots on each side for adding accessories.

Above: The AP5-P’s cold hammer forged barrel is threaded for direct attachment of a suppressor, but the quick-detach tri-lug mount is a better option. Our tri-lug-equipped Omega 9K snaps into place with ease.

Since my AP5-P was now an SBR, I could also add a stock. I considered a few options, including the original-style side-folder, but decided on an even more compact telescoping stock from Swiss manufacturer Brügger & Thomet. B&T has a long history of producing high-end aftermarket parts and suppressors for H&K guns, and even made their own clone of the MP5 called the B&T 96 (like I said, at one point everybody was using the MP5). This B&T telescopic stock collapses almost completely flush with the rear of the receiver and snaps out to any of the five positions in the blink of an eye. It’s surprisingly sturdy and comfortable but comes at a steep price of $518 MSRP.

Above: standard MKE pistol handguard and Gibbous Outfitters vertical grip with integrated SureFire tape switch cutout.

I also wanted to try a modern side-folding option, so I picked up a Picatinny MP5K stock adapter and SS-8R skeletonized aluminum stock from JMac Customs. The JMac stock fits the MP5K perfectly and even has the option of adjustable cheek riser attachments.

More Upgrades

The AP5-P comes with a pistol grip/trigger housing that mimics the style of early MP5s, complete with finger grooves and a contoured thumb rest (sometimes called the SEF lower due to its original selector markings). Later in the MP5’s production, H&K switched to a smoother trigger housing without finger grooves on the pistol grip. This is usually referred to as the Navy lower, in reference to its use on the MP5-N designed for a U.S. Navy contract. Having tried both styles, I decided to replace the lower on my AP5P with a Navy-style lower from HKParts (HKP-02463).

Above: From top to bottom: B&T telescopic stock, standard MKE buttplate with sling swivel, JMac Customs Picatinny stock adapter and SS-8R stock.

Since I was already replacing the trigger housing, I figured I might as well upgrade a few other components. The stock trigger was replaced with a much lighter and more precise drop-in two-stage trigger assembly from Timney Triggers — it’s a night-and-day improvement, and an upgrade I believe every semi-auto MP5 deserves. While installing the trigger, I also installed a new HKParts U.S.-made ejector lever (HKP-19660), ejector lever spring (HKP-00059), and enhanced safety selector (HKP-18065).

Fine-Tuning Bolt Gap

Bolt gap — the tiny sliver of space between the rear of the bolt head and the front of the bolt carrier — is a topic that H&K enthusiasts will debate in agonizing detail online. In simple terms, it should be within H&K’s recommended spec of 0.010 inch and 0.018 inch, as measured by sliding a feeler gauge into the bolt while it’s in battery with the hammer forward. Ideally, you’ll want to split the difference at 0.014 inch, since the gap will shrink over time as components wear.

Above: From the factory, the AP5-P’s bolt gap was right on the edge of the ideal tolerance range. These HKParts +2 rollers, along with a new pin and retainer spring, adjusted it for better long-term performance.

Out-of-spec bolt gap can lead to malfunctions and, in rarer cases, can even cause damage to the inside of the gun’s receiver over time. After learning this, I decided to check it on the AP5-P. It measured at 0.010 inch — right on the edge of the recommended spec and seeming likely to go out of spec after a few years of frequent use — so I decided to calibrate the gap by adding a set of U.S.-made +2 rollers from HKParts (HKP-19423). I installed the rollers into the AP5’s bolt along with a new HKParts roller pin (HKP-00066) and roller retainer spring (HKP-00068). Measuring again showed exactly 0.014 inch on the feeler gauge.

Finishing Touches

Although the HK-style iron sights work well, I still prefer a red-dot sight for better spatial awareness and faster target acquisition. I picked up an MFI Ultra-Low-Profile red-dot mount from HKParts (HKP-17962) and paired it with an Aimpoint ACRO P-2 sight on a B&T Skeleton QD mount. This setup allows me to look straight through the optic mount to use the original irons or lift my head slightly to use the red dot.

Mounting a flashlight on an MP5K is tricky due to the limited space and lack of accessory rails, so I spent quite a while researching options. Eventually, I came across the MP5 Front Sight Mount from Gibbous Outfitters, a small specialty manufacturer based in Oregon. This clever attachment system clamps a SureFire Scout-style weapon light body onto the MP5’s front sight post, using two screws and a titanium plate to keep it securely in place. Gibbous Outfitters offers another variant of the mount that holds a SureFire pressure switch on top of the cocking tube for easy access; it even has a retaining clip to keep the switch cable neatly stowed.

I used an Arisaka Defense 300 series light body, Malkoff Devices E1HT light head, and SureFire UE07 tailcap/switch assembly with the Gibbous mount. Gibbous Outfitters also makes an MP5K vertical grip with an integrated pressure switch mount for users who’d rather activate their light with a squeeze of the support hand, as opposed to placing a thumb over the cocking tube.

Above: A Haley Strategic FlatPack Plus backpack fits the AP5-P like a glove, even with a 30-round magazine installed. It’s no Operational Briefcase, but it serves as a great range bag.

With the light mount and optic installed, the standard rounded cocking handle was a little difficult to access, so I added an extended, knurled charging handle from HKParts (HKP-16999). I also picked up a single-point sling (HKP-02644) to replace the two-point sling included with the AP5.

Every SMG or PDW is more enjoyable to shoot with a suppressor, so I topped off my AP5 with a SilencerCo Omega 9K. With SilencerCo’s low-profile tri-lug mount, attaching it to the gun is as simple as a quick press and twist. The compact Omega 9K feels like a match made in heaven for an MP5K.

Finally, I needed some more magazines to keep my AP5-P fed with a steady supply of 9mm ammo. Overwatch Precision makes some excellent 32-round MP5 mags. They’re molded from sturdy polymer with slip-resistant texture, and unlike standard MP5 mags, they can be loaded with 30 rounds and inserted on a closed bolt. Better yet, at $20 each, they’re vastly more affordable than MKE mags ($70 MSRP) or H&K mags ($80 MSRP).

Pistol, SMG, or PDW?

You’ve probably seen the MP5K referred to as a PDW, short for Personal Defense Weapon. H&K themselves currently offer a variant called the MP5K-PDW. So, what does this term mean?

By the most modern definition, a PDW is a compact submachine gun-style weapon that fires a high-velocity, bottlenecked, rifle-style cartridge. The FN P90 (5.7x28mm) and H&K MP7 (4.6x30mm) are good examples of the category, offering excellent concealability and high-velocity, armor-penetrating capabilities. By this specific definition, the MP5K is not a PDW solely due to the 9mm round it fires. It’s just a compact submachine gun. However, since civilian MP5K variants (e.g., H&K’s SP5K or the AP5-P) are semi-auto only and lack select-fire capabilities, they’re not exactly SMGs either.

Legally, my MP5K clone started life as a pistol with no buttstock and no vertical foregrip — two modifications that aren’t legal in the U.S. unless the weapon has been registered as a Short-Barreled Rifle (SBR). So, that’s exactly what this AP5-P is now: a registered SBR that happens to be chambered in a pistol caliber.

Would I call this a PDW? Sure. Aside from its caliber, it fits the modern definition to a T, and it was designed to fill the same role as most PDWs. Many other 9mm weapons fall into this category, such as the B&T MP9 and Russian PP-2000. Only the most pedantic keyboard commandos will take issue with this designation, and I don’t really care what they think anyway.

Closing Thoughts

As a kid growing up in the ’90s, the MP5K was immortalized in my mind by movies such as Terminator 2, Air Force One, and The Matrix, as well as video games including GoldenEye 007 and Rainbow Six. There were lots of weapons that received similar pop culture coverage that didn’t live up to the hype in reality (looking at you, Franchi SPAS-12). Just as you might be disappointed by meeting your heroes, you might not always enjoy shooting their signature guns. Thankfully, the MP5K is just as much fun to shoot as I had hoped, and the AP5-P captures that same look, feel, and performance. The modifications shown here add a new level of modern refinement to this nearly 50-year-old classic weapon.

Above: The HKParts Navy-style trigger housing eliminates the finger grooves and contours of the original SEF pistol grip. I find it more comfortable, and I prefer the modernized look as well.

So, to address the elephant in the room, should you buy a new German-made H&K SP5K or a clone like the Century Arms AP5-P? That’s a question only you can answer. On one hand, an original H&K will be manufactured using the latest tooling and quality control procedures; most clones are using old tooling that may be worn after decades of use, or tooling that has been replicated. On the other hand, the MSRP for a new H&K SP5K-PDW is a staggering $3,389. H&K also has it listed as a “limited production” model, and many sell for above MSRP due to scarcity.

MSRP for the AP5-P — including two 30-round mags, sling, optic mount, quick-detach flash hider, cleaning kit, and hard case — is $1,360. H&K’s product page confidently asks, “Who wants a copy when you can own the real thing?” When the real thing (or at least the “civilian sporting version” of it) is roughly 2.5 times the price of a functionally identical clone made with original tooling, the answer to that question is “a lot of people, including me.”

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Editor's Note: This article has been modified from its original version for the web.

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Patrick McCarthy: Patrick McCarthy is the Editor of RECOIL OFFGRID. He currently resides in Arizona, and enjoys hiking, camping, shooting, and snapping photos along the way. You can follow his latest projects on Instagram at @pmccarthy10.