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This is a review of KSC’s GBB version of the Heckler & Koch Mark 23 “SOCOM”, and will detail my likes, dislikes, and the unique bits of this interesting pistol.

First Looks

This is the KSC MK23 GBB pistol – also known as the “SOCOM”. This gun has a few things that set it apart from others; some good and others not so good. But regardless, it’s a nice gun with a great feel and presence to it. It also has some seriously cool accessories available for it.

It comes with a manual, cleaning rod, magazine, a tube-and-ramrod loading tool, hop-up adjustment tool, allen key, and some BBs.

This is a large and hefty gun, but unlike the KWC Desert Eagle , it’s much more ergonomic and comfortable to hold. I attribute this to the fact that the grip doesn’t feel as thick/wide as on the Desert Eagle.

The body is mostly flat black ABS, though there are some metal parts on the gun and inside it. The magazine is all metal. The trademarks are all present on the gun.

There are also two versions of the gun. The plain ABS version weighs about 1kg, and the Heavyweight version has a sort of reinforced ABS slide, and weighs in at just under 1.2kg. Both otherwise function the same – though the heavyweight version has a slightly harder recoil due to the increased mass of the slide.

The build quality is very nice, and it reproduces the original’s looks all the way down to the fake polygonal rifling, and the tiny little green O-ring on the barrel, visible once you pull the slide back. The MK23’s double-stage recoil spring is also faithfully reproduced. Even the shell ejector arm is spring-loaded, even though it doesn’t *do* anything! (Actually it helps hold in some internals, but they could easily have left out the spring-loading. Instead, KSC put it in to make it more like the real thing).

If you’re interested in more information about the real MK23 (and the bits like the O-ring and the recoil spring), then visit the following links:

Basic Info about the MK23:

Excellent Info about the MK23, with lots of pictures:

.MOV file of the real MK23 firing (1.31 MB)


Basic operation of the gun is much like any other Gas Blowback. Fill the magazine with gas and BBs, pull back the slide, let it return forward (chambering a BB in the process), and it’s ready to fire. On the last shot, the slide remains open. You may then remove the magazine, insert a fresh one (or the reloaded one), and release the slide by releasing the slide catch.

The trigger pull is exceptionally nice and smooth; more on the trigger assembly later. The safety is ambidextrous, but I found it to be a bit stiff.

Some of the things that make this gun a little different than other GBBs include:

  • Unique mag release catch
  • Threaded barrel
  • Dual-stage recoil rod and spring
  • No separate takedown lever
  • Single or Double-action operation
  • Working decocking lever
  • Unusual (for an Airsoft gun) hammer assembly

Mag Release

The mag release is located at the junction of the bottom of the finger guard where it meets the grip. It is ambidextrous. Some people say they are prone to hit it by accident, but I have found the exact opposite. It is extremely comfortable to hit the mag release like in this picture, with the tip of my middle finger pushing down.

Threaded Barrel

The barrel protrudes from the slide and is threaded, allowing easy and adapter-free attachment of a SOCOM suppressor.

The outer barrel is ABS – not metal. So be careful not to cross-thread the suppressor as you attach it.

Dual-Stage recoil spring; Takedown Lever

The recoil rod and spring are inside the slide in this image. There are two springs on the recoil rod: a large exterior one and a smaller, tighter one inside. This faithfully reproduces the real MK23’s recoil rod assembly.

You can also see that the takedown lever and slide catch are one and the same (like 1911 style guns). Remove the slide catch to remove the slide.

Single or Double-Action

If the hammer is cocked (either by racking the slide manually or from blowback) you can pull the trigger to fire. This is normal operation for an autoloader. However, you can also pull the trigger to fire if the hammer is NOT cocked. This can be handy if you have been carrying the gun uncocked but loaded. You need not pull back the hammer manually before firing – simply pull the trigger.

Decocking Lever

Another handy feature is the decocking lever. If the hammer is cocked, pull the lever all the way down with your thumb, then let it back up. The hammer will uncock safely.

Not many guns have decocking levers, and out of the ones that do the Airsoft versions tend to not be functional.

Hammer Assembly

The hammer assembly is unlike any other Gas gun I have seen. (Though I admit there are many I have not yet taken apart.)

In the Mark 23, the hammer hits something very much like a firing pin. This firing pin strikes the gas release valve on the magazine to release gas. In essence, the operation is much closer to that of a real gun.

In the other gas guns I have seen, there is one hammer assembly with something more like two hammers – one is external and provides the inertia. The other is internal – the one that actually drives into the magazine’s gas release valve. It’s connected to the same hammer assembly.

For a better idea of how other gas gun hammer assemblies work, take a look at the G18C’s hammer assembly. Unlike some pistols, the Glock has an internal hammer but the basic operation of the assembly is the same.

Filling with Gas

The gas fill valve on the bottom of the magazine is like any other gas gun magazine. The KSC MK23 SOCOM can take Green Gas (TOP gas, Jet gas, HFC22) just fine. In fact, it works much better on green gas, I find. On duster (HFC134a) it doesn’t perform as well. The MK23 seems to eat more gas than usual for a GBB, but nothing excessive.

For tips on effectively filling with gas, you can check out the gas filling section of my Glock 18C review.

Remember that once the magazine is filled with gas, the magazine should be left to warm up to room temperature (2-3 minutes wait) before being used. The magazine is cooled by the act of filling, and letting it warm up helps keep the valves and seals working well (and lasting a long time). Also, the warmer the compressed liquid gas is, the faster it can convert into gaseous form, which is what makes the gun work. The colder the magazine, the harder that is for the gas to do.

Loading with BBs

Loading the BBs is done via the standard tube-and-ramrod setup. You can load the BBs one by one by hand as well. I find it cumbersome compared to the newer mag designs that allow you to pull the spring down and pour BBs in, personally.

Firing the Mark 23

First thing is to push the magazine into the bottom of the gun until it clicks. If it doesn’t fall out, you’ve done it right.

Now pull the slide back all the way (if you look inside the now-open breech you should be able to see the BB at the top of the magazine) which will cock the hammer. Then let go of the slide and it will slide forward and lock into place. When it slid forward, it scooped a BB from the magazine. The gun is now ready to fire.

If you wish, you can use the decocking lever to uncock the hammer, leaving a BB in the chamber. You can then either pull the hammer back manually, then fire (Single-Action); or pull the trigger back to cock the hammer and fire in one pull (Double-Action).

The MK23 has a nice blowback, but not as strong as some guns. This is probably due to the size of the gun as well as the recoil spring. The blowback is strong enough that I find it satisfying, without being so strong as to interfere too much with accuracy. (The stronger the recoil, the more time it takes to line up a second shot – but a weak recoil is no fun at all!)

The trigger pull is very smooth and clean, even when firing in double action (trigger pull cocks the hammer and then fires). This makes it much more comfortable to shoot, and helps accuracy.


POWER:The MK23 fires no harder than any other stock Gas blowback I have fired. At 3 feet (about 1 meter) away with a .20g BB, the MK23 punctures one side of an empty coke can and the BB remains in the can. According to the Poor Man’s Chronograph, that corresponds to 290-310 fps. There isn’t too serious of a dent on the second side of the can, so it’s likely firing at the low end of that range.

Like most gas guns, power can be increased most easily by a highflow valve on the magazine and a strengthened hammer spring.

GAS USAGE: The MK23 seems prone to a cooldown effect when rapid-firing an entire mag, especially when using duster/HFC134a. Cooldown (which results in lower and lower power shots) also manifests itself in higher gas consumption.

ACCURACY: The MK23 has some advantages here – it’s a solid gun and fires as well as any decently-made GBB. However, in addition it also has a smooth and light trigger pull and the recoil isn’t excessive. Both of these help to make those extra-accurate shots happen.

Adjusting Hop-Up

To adjust the hop-up, pull the slide back and lock it. Then look into the breech, you’ll see the opening into the barrel. Notice the two notches.

You use the hopup adjustment tool to turn the inner ring with the notches like a screwdriver. Clockwise for less, counterclockwise for more.

Care and Cleaning

To take apart the Mark 23, remove the magazine then do the following:

1. Pull the slide back only far enough to line up the notch with the slide catch. A picture is worth a thousand words.

2. Push the slide catch out from the other side. It should come out fairly easily.

3. Pull the slide forward and off. You can then remove the recoil rod and the barrel assembly.

To re-assemble, perform the steps in reverse. This is probably the easiest and most straightforward disassembly I have ever had the pleasure to do.


There are quite a few accessories for the MK23, not the least of which are custom holsters. Like most other GBBs, the “Standard” accessories like metal slides and barrels as well as high flow valves, enhanced springs, etc are all available.

The most common accessories are the SOCOM supressor, which threads onto the end of the SOCOM and actually works; and a LAM unit.

The LAM units contain everything from a flashlight, to a laser, to both. They fit onto the front rail of the MK23 and thread into the front of the trigger guard to anchor in place. They look pretty stylish, but can be very expensive. There are even holsters made to hold an MK23 with a LAM unit, and even one that also has a pocket specifically for the supressor as well.

The Mark 23 holster can also fit a Desert Eagle, and in a pinch, a MAC-11.

The Not So Good

There are two high-stress parts I know of in the KSC MK23.

  • Part #66 is a crucial part of the hammer assembly and can wear quickly, especially if you are using higher-pressure gas like Propane/Green gas instead of Duster. Reinforced part #66’s are available.
  • Part #30 has been blown off on at least two other MK23’s I have seen. Possibly a result of using high pressure gas like Propane.

Defining Characteristics

Excellent attention to detail, beautiful construction, good shooting experience, long-term durability concerns with higher pressure gas.

Things I Like

  • Very sturdy construction, solid feel, nice finish
  • Very smooth action, light trigger pull
  • Satisfying blowback
  • Simple and efficient field stripping
  • Despite part #66 being high-stress, I really appreciate the unique hammer assembly.
  • Functional decocking lever is a wonderful thing
  • Attention to detail even in little things like fake rifling, the green O-ring, and the striker under the hammer that actually moves in and is spring-loaded. Even the shell ejector arm (which is nonfunctional) is spring loaded purely for the sake of authenticity.
  • Threaded muzzle is standard (even if it is plastic)
  • Excellent ergonomics, fits me very well (though I have slightly larger than average hands)
  • I like the HK style newfangled mag release

Things I Don’t Like

  • Gotta watch those plastic threads when screwing on a metal supressor
  • Fake LAM units (with the exception of the cheapo one from the TM MK23 NBB package) are unreasonably expensive
  • Seems prone to wear and tear on some internals (part #66 and part #30 in my experience)
  • It seems gas-hungry, but not excessively so.
  • It is prone to a noticeable cooldown effect when rapid-firing, causing less and less powerful shots. This is most noticeable when using duster/HFC134a, rather than green/TOP/HFC22 gas.
  • It costs as much as some Western Arms guns (the Cadillacs of GBBs)


This is a nice gun, despite any shortcomings. It has a lot of attention to detail in the design and construction that is not hard to appreciate. It has good performance, and excellent handling and operation.

Long-term reliability, however, seems to be an issue with higher pressure gases especially. I’ve done some gun repair and servicing, and it seems to be a commonly malfunctioning GBB. It is also one of the more expensive gas guns out there.

But the reliability at least is a long-term issue that CAN be addressed with care, cleaning, and if necessary – reinforced parts. It’s not a reliability issue in the sense that you don’t know from one trigger pull to the next whether it’s going to shoot or not.

Does the bad and the cost outweigh the good? That’s up to you. Personally, I think that the good points balance the bad points and the high cost – but only just. It’s a nice gun to shoot and a great gun for a collection, both for the excellent body and looks and detail, as well as the inventive internal design.

If you’re looking for “just a gun”, then you’re probably better off in the long run with something a little more rugged and proven – and cheaper. You could probably pick up a lesser but more rugged and practical GBB plus an extra magazine for around or less than the cost of a new MK23.

Also, the TM MK23 may be right up your alley. Follow that link for a review.

Mark 23 Parts Diagram