Heckler & Koch Mk23 - KSC

I have owned a number of KSC H&K Mk23s over the years, but the only review of one on this site is a comparison test with the TM NBB version that is a little long in the tooth in style and content, having been originally written as far back as 2003.

The H&K Mk23 was designed from the outset as an 'Offensive Handgun', for use by US Special Forces in an attack role, rather than as a backup for troops with larger weapons as their primaries.

The Mk23 is considered by many to be too large (and .45 H&K USP Tacticals offer nearly as much in a much more manageable package), but it is an imposing and impressive handgun.

KSC Mk23 is a great replica of the huge Special Forces pistol

My KSC Mk23 is upgraded in that it has a Shooter's Design metal slide and outer barrel kit, along with upgraded hammer and recoil spring and, although originally a Hardkick Model, has the 2005 blowback engine from a later gun I acquired for spares.

So, whilst not an example of a KSC Mk23 out of the box, it's a fair representation of the kind of upgrades many owners (and some retailers) will carry out.

In the Box

The KSC box is the traditional style from my pre-2005 Hardkick gun.

There is a very detailed front cover over a polystyrene base, which holds the gun, hopper, tube and rod loading tool (like the KSC Berettas and some WA guns), a few BBs, a manual and a hop-up adjustment tool.

As my gun is a late Hardkick version, it features the later style rotary hop-up, which continues on the latest MK23s and there's an addendum sheet to explain how this is adjusted.

Usual collection of KSC bits - Slot for silencer hidden by manual.

There's a slot in the box, too, for a silencer, which is a good idea.

The most recent guns come in a different box, with a dark Olive drab colour outer shell and a more solid polystyrene bed, very much like that of other recent KSC/KWA releases like the USP and the 1911A1.

First Impressions

Even without the SD slide and barrel, the first impression of a KSC Mk23 Heavyweight is excellent.

The finish and detailing are excellent, with the polymer frame featuring a slight rubberised feel.

The heavyweight slide is typical of the metal/abs mix material used on KSC and WA guns, being grey and matt in finish.

ABS guns are much shinier in slide and frame. Some say the ABS frame is more realistic to the real thing and it's certainly true of the Commercial Mk23 (KSC also make a replica of this, btw).

Heavyweight frame is a slightly rubberised matt finish - Slide here is aftermarket Shooters Design slide

Trades are good, although as often the case with KSC they are a little shallow and fine, but the SD slides address that issue.

The gun is very large, but offers excellent ergonomics (as long as you don't have small hands) and even without the metal slide is well over a kilo in weight.

Ergonomics remarkably good for such a large gun.

Standard metal parts include sights, trigger, hammer, safety, decocker, slide lock, magazine release and recoil rod.

Closer Look

This a gun of two parts really.

Everything in the frame is KSC and everything in the slide is Shooter's Design.

The good news is that both are high quality. The heavyweight frame is slightly rubberised to the touch (you may not even notice it unless you've handled other GBBs) and is very heavy.

The finish is good and the hammer, slide lock, safeties and decocker are all metal and (in my experience - I've seen a few reports of slide locks breaking) up to the job.

The hammer has a low profile, rounded spur with grooves on the tip to facilitate thumb cooking. The slide lock has grooves on the upper rear edge and the decocker has grooves on the tip, all to aid operation.

The trigger is metal too, with a broad, smooth face. Behind the trigger, running either side of the rear of the trigger guard, is the ambidextrous magazine release lever. It works well, but on this gun the magazines need a good hard shove to engage correctly. Once there, though, they never come loose.

Markings impressively accurate and complete in standard and SD slide form

Under the front of the frame is a silver plate with the id "23-0747" on it. Either side of the plate is "Heckler & Koch Inc." and "Sterling VA". Ahead of this is a small JASG logo.

Underneath the trigger guard is "Warning Refer to Owners Manual" and when the decocker is pressed down, a KSC logo is visible, the only one on the whole gun - Full marks to KSC!

Only KSC marking is concealed under decocker at rest.

The grip is marked "Heckler & Koch GmbH Made in Germany" at the top right. and "US Pat.5.309.815" at the bottom right. On the left, the grip is marked "HK .45" on the lower part.

seam is faint and acceptable on replica of polymer frame. Note markings on mag base and under trigger guard.

The Shooters Design slide (like the Heavyweight ABS/Metal Dust mix KSC standard version) is marked "HK USSOCOM Cal. .45" and "23-0747" (followed by a small capital B in a circle) on the left side.

On the right, the chamber is marked "HK Cal. .45" with 23-0747 and the B below it. Ahead of the slide lock on the right is the serial number XK202100.

The markings on this SD slide are much deeper and more distinct than those on an original KSC slide (a common complaint about KSC guns).

Trademark Mk23 O-ring present on KSC GBB - Not on the TM NBB

The KSC guns (unlike the TM NBB) have the trademark green O-ring on the barrel (if you fit an SD barrel, you need to swap it over, so the green ring here is the KSC one) and, of course, you gain the advantage of a metal thread for the 16mm silencer. Unlike TM, KSC don't fit a metal tip to their barrels as standard, so you risk damaging the plastic thread every time you fit or remove a silencer on the standard gun.

Proper Mk23 silencers double the length of the gun - This is a G&G SOCOM silencer.

A frequent complaint of the KSC Mk23 is that the blowback is sluggish. I always find this a rather odd complaint, but certainly early guns could suffer from the heavy slide compressing the recoil spring if held upright and an upgraded recoil spring, whilst essential with the heavier metal slide, is a worthwhile fitment on a standard KSC Mk23.

Big gun and heavy, too, but easier to handle than most 'hand cannons'.

In reality the KSC Mk23 here cycles in 9/100ths of a second, which compares well with most other GBBs - How quickly can you blink, or click your mouse button twice?

The heavy weight of the slide (even in HW plastic form) which slows the cycling does reward you with much more felt kick when the gun is fired. Personally, I find the heavy, slightly muted kick (a design feature of the real Mk23, so properly replicated) vastly preferable to the snappy lapdog action of, for example, a TM Hi-Capa.

Sights look like tritium night sights, but do not glow in the dark on my gun. Note hammer's grooves.

The sights are pretty good, but although they look as though they may be luminous in daylight (when the dots are a pale greenish-white) they don't seem to be in the dark. A dab of luminous paint would solve the matter, but in daylight bright white dots (as on the TM NBB) would be more usable (if less realistic).

Both sights are dovetailed into the slide, allowing adjustment for windage, but there is no adjustment on the rear sight for elevation, as with the actual gun.

The rail on the front of the frame is a unique size for the Mk23, so you will need Mk23 specific parts (The TM LAM fits as do the more realistic, and more expensive, aftermarket replica LAMs) or an adaptor to fit 20mm accessories.

Shooting Impressions

So is it a hefty beauty pageant contestant or can the Mk23 walk the walk, too?

Click on image for bigger version in separate window.

Carrying out my standard 5m/6 round, off hand test, I was able to place 5 shots in a 40mm diameter, impressive accuracy by any standards (The second set of 6 saw 4 shots almost in one hole, shooting without support and with a G&G SOCOM silencer fitted!)

At longer range, the hop was set a little low for .25g BBs (easily set without disassembly with the rotary tool provided), but I was still able to repeatedly hit a postcard sized target at 70ft, getting a pass on the 'Pig Test'.

Over 10 shots, my KSC Mk23 averaged 316 fps (using Propane gas) indoors (at 26C), which equate to around 280-285fps at 20C based on prior experience.

Shot      FPS
1 320.0
2 319.0
3 318.6
4 314.4
5 314.4
6 317.8
7 311.0
8 318.2
9 318.6
10 311.6

Good power is a common feature of most KSC guns and all the KSC Mk23s I've owned have delivered in this respect, although I remain unconvinced as to the value of the upgraded hammer spring (It was fitted to this gun when I bought it).

Trigger pull was 680g (24 Oz), which is a lightish pull for a GBB. The 2005 ABS gun I used to own, seen at the bottom of the review, delivered an even lighter 585g pull.

Take Down

As expected, take down is realistic.

After removing the magazine, slide the slide back until the disassembly notch in the slide (furthest forward on left side) is aligned with the front part of the slide lock and push the slide lock through the frame from the other side (you might need to get a finger nail under the slide lock and pull it through), completely removing it from the frame.

Once this is done, the slide, barrel and recoil rod will slide off the frame.

Field strips like a USP - Note original style recoil rod which is close to real steel design - 2005 model guns have a straight rod

At this stage, the recoil rod can be removed by pushing it gently forward and down and then back.

The barrel should be slid forward and down, once clear of the nozzle.


I'm a big fan of the KSC Mk23, especially in Heavyweight form.

I find the slower, but forceful kick, much more realistic than the snappy but light kick that some people seem to prefer.

A different KSC Mk23 - This is a 2005 ABS model with the SD Phase 2 slide - Note the shiney black finish of the frame.

It's not a perfect gun, being too big for some and, in ABS form at least, being prone to slide breakages around the slide lock and I've heard of slide locks and recoil rods breaking on the 2005 models.

However, it is a truly excellent replica of the Heckler and Koch hand cannon (even better with a quality metal slide, Prime also make one now) and delivers in spades in terms of power, kick and accuracy.

My recommendation is that everyone tries one.

Addendum - The KSC 2005 models

In 2005, KSC launched a revised Mk23.

This featured a number of small changes, aimed at dealing with the criticism of slow cycling.

Firstly, the accurately replicated recoil rod and spring were replaced with a simpler system with a buffer.

Revised 2005 style recoil rod shown lower.

Secondly, the magazine was changed to have a slightly larger reservoir.

Finally, the blowback engine was modified to have a greater volume (the main reason for enlarging the magazine reservoir being the gun now uses more gas per shot).

Personally, I do not believe the changes make any significant difference. I can detect no difference in kick between the blowback engines in my two (now) Mk23s, equipped with SD metal slide kits and even combined the engine or recoil rod delivered no more than a couple 1/1000ths faster cycle time on a 2005 model in standard ABS (with a very light and fragile slide).

Otherwise the 2005 and older models are indistinguishable (some claim 2005 ABS models are heavier than earlier ones, but they look identical, so I am doubtful - both seem very light and I would never recommend an ABS model over a HW version, the price difference is small and worth it tenfold). Other than the parts mentioned, there are no differences and the blowback engine and recoil rod from 2005 or older guns will work in either with no modification.

Weight : 1240g as tested (365g Magazine)
1180g in stock heavy weight form.

Realism : *****
Quality : *****
Power : ****
Accuracy : ****

Real Steel link at World Guns
The H&K Mark 23 Owners Guild website - loads of information on the real Mk23.

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