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Maruzen MP5K A4
  • Manufacturer 
  • Model 
     MP5K A4
  • Capacity 
     30 / 50
  • Weight 
  • Power 
  • Power Source 
     HFC134a ONLY
  • Blowback 
  • Hop-up 
  • Shooting Mode 
     Semi, Full Auto
  • Construction 
     ABS Plastic, Metal


+ Excellent finishing and build quality + Good blowback feel and nice crisp 'rat-tat-tat' on firing + Decent accuracy (CQB) + Affordable price


- No "empty magazine" lock catch - Mediocre range since limited to HFC134a propellant - Use of HFC22 breaks the gun immediately - DO NOT USE! - Showed some cool-down effects - Fixed hop-up


Great alternative to the AEG MP5K. Good full auto blowback fun for recreational shooting, though not mature (ie. developed) enough to take out onto a large scale skirmish due to limited range and unknown upgrade potential (at the time of this writing).


With airsoft becoming ever more mature and new ideas being created for skirmish scenarios, many players are beginning to appreciate the fun of close quarters skirmish battles with limited ammunition - simulating real life hostage rescue situations, witness protection programs, while some have begun to explore "suit skirmishes". For those unfamiliar with this last one, some experienced players have long started battling it out in dark suits, shirt and tie, brandishing Glocks, M11s and other compact tactical weapons. Frankly we're still waiting for someone to play out an Al Capone gangster hit with a Tommy Gun!

At least for myself, the experience of skirmishing with a blowback weapon has always been more alluring than firing an AEG (motor whirring and no blowback kick). Until now, my options were limited to the KSC TMP, the WA and then the KSC M11, Maruzen KG9 and Uzi Pistol. As such, Maruzen's decision to release a gas blowback version of the popular MP5K was music to my ears.

The MP5K denotation is short for Machine Pistol "Kurz", which means "short" in German. It was introduced in 1976 and was intended to address the South American market, which at the time was seeing an increasing demand for concealed firearms to protect dignitaries and other important officials. The MP5K is of course, a variant of the original MP5 machine gun series. For those of you who haven't read our review of the Tokyo Marui MP5, there's more history about MP5s to be learned there.

The MP5K was never a big hit and only in 1991 when a folding shoulder stock was added (the MP5K PDW) did sales of the MP5K take off. Choate manufactures the PDW shoulder stock for Heckler & Koch, and the stocks are applied to the K models in the United States. The addition of the stock made the MP5 much more controllable and the incorporation of the standard 3-star lug barrel made it easier to attach silencers and other accessories.

The MP5K is a perfect weapon for VIP security detail since it is easily concealable under a coat, an attaché case, a soft carry bag, or in a vehicle's trunk, under-seat space, or glove box. Capable of 900 rounds per minute, the MP5K represented a high firepower-to-size ratio. In some heated situations, clearly a handgun is not enough.

Using a tactical nylon carrying sling, the MP5K-PDW can be carried comfortably underneath either arm. Loaded spare magazines can be carried under the opposite arm. Simply thrusting the weapon away from the body automatically extends and locks the stock in place for immediate use. A convenient quick release allows the weapon to be rapidly removed or reattached to the carrying rig.

The Maruzen MP5K is constructed of high quality ABS plastic with an assortment of metal parts. The gun is constructed in a sturdy manner and feels very similar to the Tokyo Marui MP5K AEG in heft. Metal parts include the front sight, windage and range adjustable open rear sight, the magazine, trigger, cocking lever (but not the cocking tube), magazine release, and rear stock plate with sling mount. Observant readers will already notice the hollow pistol grip to defiantly declare "look, no motor - I'm not an AEG!".

MP5K in action from the movie Navy Seals, 1990 Orion Pictures
The real steel MP5K with Navy trigger group
The MP5KA4 is a lethal yet compact weapon

Similar to gas blowback pistols, propellant gas is charged into the bottom of the included detachable 30 round magazine. Loading the BBs is similar to a gas pistol, where the user pulls down on the magazine butt-plate and pours the BBs in stacked formation. An optional 50 round magazine adds greater capacity, though is a little odd looking since it appears Maruzen chose to manufacture the longer magazine as 2 segments, leaving a seam halfway down the magazine.

Unlike the real MP5K, the Maruzen version fires from an open-bolt position, and pulling back on the cocking lever for the first round opens the bolt (keeping it open on each cycle). We found that Maruzen designed the cocking lever in such a manner that it never contacts the body of the gun, which means that you can snap the cocking lever forward without fear of breaking it off.

The dust cover is plastic but the internal framework is metal to increase durability. During firing, the dust cover blows back rapidly but the cocking lever does not move.

The ambidextrous firing selector is made of plastic but has a better tactile feel than the one on Tokyo Marui MP5s. Maruzen's MP5K is true to form and the claw mounts designed for Tokyo Marui's MP5's will fit onto the Maruzen MP5Ks upper receiver to allow installation of scopes and accessories. The fitting is a little tight however, and may require the installer to give it a strong nudge, risking scratching up the receiver a little bit.

Front metal sight
The standard 30 round magazine and the 50 rounder
Ambidextrous selector switch for easy access

Firing the MP5K is a blast with extremely high cycle times and good blowback feel. There is some cool-down effect though if you try to empty 50 rounds in one trigger pull; slowdown becomes quite apparent in the last 5-10 rounds. Unfortunately at the time of this writing, the weather was getting cold so ambient test temperatures ranged from 13 degrees to 18 degrees Celsius. We cannot speculate whether the cool down effects would exist on a hot 30 degree day though it likely would have been reduced if not completely eliminated.

Pivot forward to disassemble the MP5K It's clear through our tests with this latest release that Maruzen is keeping its guns economical by cutting some corners. The corners came in the form of a fixed hop-up system, and the inability of the gun to lock back the bolt once the magazine is empty. Just like the Maruzen Uzi-Pistol, the MP5K keeps on cycling even all its doing is "blowing smoke". However the difference is sound is discernable so shooters won't go too long before noticing.

Our tests with HFC134a proved reliable and delivered 230fps - 240fps of power (0.5 joules). When we tried to use the higher power HFC22 propellant, we were met with another disappointment; the extra power unseated the blowback piston and we jammed the gun on the first round. After disassembling the gun, we found the problem and promptly corrected the jam. Despite the non-permanent damage, this little escapade was a clear warning that HFC22 was not an option. Our in house specialists have inspected the mechanism and surmise that reinforced parts may allow this in the future. Until aftermarket parts are released for this cause, we recommend only using HFC134a.

Metal stock plate makes a solid sling mounting point Having said that, the effective distance and power was acceptable enough for CQB skirmishing, thanks in part also to the high rate of fire. Effective range was clocked at 50 feet while maximum travel range was approximately 80 feet, with the BB dropping off fairly rapidly towards the end. Accuracy is decent from 10 feet with a variance of 1 - 2cm. The standard sights are good enough, though the MP5K really came to life after we cropped on a SWIFT red-dot scope for added precision. Unfortunately as of this writing, there is no easy way to attach a silencer, though no doubt a solution will make it to market very soon.

Field testing the MP5K confirmed my personal belief that airsoft will gradually evolve back towards gas blowback skirmishing. As I entered our mockup "hostage situation" with the MP5K lined up high against my line of sight, taking out targets with 3 round rapid blowback bursts is simply much more gratifying than squeezing the trigger on an AEG and waiting for the bullet hose to arrive. The blowback feel and sound simply add a lot more realism and who cares if it only kicks out 240fps of power from a range of 10 to 15 feet, it was enough to sting my opponents plenty. And what about the ability to keep heads down? The high rate of fire was only matched by AEGs with EG1000 motors running 2000mah batteries.

BBs are inserted into the magazine much like on a GBB pistol
Note hollow pistol grip
With the cocking lever pulled back, the gaping hole in the bolt stares back at you

With such a compact package, carrying the gun is as important as how you use it in battle. Using the MP5K tactical sling is the most efficient method of carry. Of course if you are creative, there are other methods of concealment worth exploring. No description of the MP5K would be complete without mention of the briefcase. One of the hottest set-ups for collectors, the briefcase has limited applications for VIP protection, other than being very discreet. There are some that allow you to fire the gun while carrying the briefcase in normal posture, and then there are cheaper versions that require you to reach in and grasp the gun like you normally would to fire. Briefcase guns are difficult to aim and fire and some of our readers have already tried similar contraptions with the WA M11 and the more recent KSC M11A1. One reader even sent a photo of himself running through the woods holding a briefcase in front of him. Frankly it looked rather humorous so maybe its best we simply leave that idea for the real steel users.

The first prototype of the MP5K
The Maruzen MP5K is easy to disassemble
When real steel designers run amok...

Disassembly is very easy and can be performed without any tools. Two retainer pins hold the rear stock plate in place and using your thumbs, these pins are easily pushed out and away from the receiver. Once these pins are removed, the rear stock plate literally pops out and allows the upper receiver to pivot away from the lower receiver. Be careful as you do this to avoid the cocking lever recoil spring from flying right out.

The trigger and hammer assembly is easy to inspect at this point, and cleaning is not a reach. Reassembly is just as easy and requires performing the same procedures backwards. Take care to seat the stock plate correctly before pushing the pins back into place.

Step 1: Install your MP5K in a tactical briefcase
Step 2: Run around pointing your case at people
Step 3: Surprise them (if you can still aim)

Our overall impressions of the Maruzen MP5K are mixed. No doubt it is a solid performer with good power and great shooting experience. In the words of Wildgoose, "It's a lot of fun but I still prefer Maruzen's earlier rendition of the GBB KG9". With good looks, ability to take the same accessories as your standard TM MP5, and a economical price, the Maruzen MP5K is worth the try if you appreciate full auto gas blowbacks.