Though some would disagree, the Heckler & Koch Mark 23 .45 ACP semi-automatic handgun is not a unicorn. It actually exists and can be purchased if you’ve got the coin.
The HK Mark 23 is unusual in the sense that it’s a polymer-frame build, but it was never commodified like GLOCKs or even other HK pistols because production has always been constricted.
I had a Mark 23 M723001-A5 variant for a couple of years and recently shot another one. HK builds only a few hundred of these every year, and they come in two configurations, one with two 12-round .45 ACP magazines (as tested here) or with two 10-round magazines (723001-A5). The latter can make the package suitable for some capacity-restricted states.
What you’re buying, of course, is a lieferwagen that looks like a handgun. The MK23 is 9.65 inches long, 5.9 inches tall, 1.53 inches thick at its widest point, and weighs 39.4 ounces unloaded with an empty magazine. With ammo, it goes all of 51 ounces; add a suppressor, and you’ve got a biceps-building loaded weight of 62 ounces and a nearly 18-inch-long OAL to slice around corners.
If you’re looking for a size reference, think Desert Eagle. Because of its history, the handgun is designated as a Special Forces offensive handgun weapon system, and it’s probably not in the size range that most people would consider for concealed carry. Think of it as a full-size-plus model.
The MK23 is 9.65 inches long and weighs 39.4 ounces unloaded with an empty magazine. Add a suppressor, and you’ve got a loaded weight of 62 ounces and a nearly 18-inch-long overall length. (Woody for TTAG)
The pistol’s background is storied, which contributes to its aura. Heckler & Koch GmbH, or HK, based in Germany, developed the MK23 Model 0 in 1991, and it would be eventually be adopted by U.S. Special Operations Command, or SOCOM.
According to the manual . . .
On May 1, 1996, the first HK MK23 pistols were delivered to the U.S. Special Operations Command for operational deployment, making the MK23 the first caliber-45 ACP pistol to enter American military service since the venerable Government Model 1911A1.
During testing, MK23 pistols met the most stringent operational and accuracy requirements ever demanded of a combat handgun. Endurance testing demonstrated a service life of more than 30,000 rounds of +P ammunition.
To meet the reliability requirement, the pistol had to demonstrate a minimum of 2,000 mean rounds between stoppages (MRBS) with both M1911 ball and +P ammunition. All pistols exceeded the 2000 MRBS with an average of 6000 MRBS.
In more than 450 accuracy test firings from a precision firing fixture at 25 meters, MK23 pistols far exceeded the government requirement, averaging 1.44 inches, with 65 groups of less than one inch.
The HK Mark 23 I recently tested was a commercial model of the U.S. Government issue MK23 MOD 0 pistol and is available in limited numbers. Designated the “Mark 23,” it’s almost identical to the MK23 MOD 0 pistol, right down to its threaded barrel. The main differences are slide markings (Mark 23 as opposed to MK23) and a barrel manufactured to SAAMI headspace specifications.
I recently saw several listings for new Mark 23s ranging from $1800 to $2165 online and used Mark 23s go for around $1700. Depending on condition, I wouldn’t be afraid of buying one of the used guns at all.
My Mark 23 arrived in a black-plastic clamshell case with four 12-round magazines, instruction manual, pad lock, and extra O-rings. I read and reread the manual, which thoroughly explained the Mark 23 pistol’s operating system. It uses a modified linkless Browning-style short-recoil system to lock and unlock the breech.
From the manual:
The rubber O-ring fits into a groove at the front of the HK Mark 23 barrel. Extras are supplied. (Image courtesy of HK)
Upon firing, the pressure developed by the propellent gas forces the slide and barrel assembly to the rear. After approximately 3mm, the locking block will stop the rearward movement of the barrel as the barrel is pivoted downward due to the engagement of the angled surfaces of the locking block with those located in the recoil spring guide rod. The locking block will disengage from the slide and the slide will continue rearward.
The extractor located in the slide will then extract the fired cartridge case. The ejector located in the frame on the left side of the magazine well will eject the fired case as the slide continues rearward and cocks the hammer and compresses the recoil spring. The slide moves forward, feeding the next cartridge from the magazine into the chamber and locking to the barrel breech.
Out front, according to HK, the captured recoil/buffer spring assembly reduces felt recoil by up to 40%. I believe some of that recoil reduction is due to weight, but it’s very easy to recover from each shot and get back on target.
The gun is smooth to operate, but tight nonetheless, and apparently HK does that by machining parts to tight tolerances and then hand-fitting them. An O-ring, which snaps into a milled groove at the front of the barrel, tightens the barrel’s fit inside the frame once the action locks up.
The O-ring lasts beyond 20,000 rounds and can be replaced by the operator without tools in seconds. Four extras are supplied. The slide release is a large frame-mounted lever on the left side of the gun. It was easy and positive to operate.
The matte black frame is made of fiber-reinforced polymer, and it supports a one-piece machined-steel slide with a corrosion-resistant finish, a frame-mounted de-cocking lever, and separate ambidextrous safety lever.
It can be carried cocked and locked in single-action mode with the safety lever on. When I transported the gun, I was comfortable with one in the pipe, the lever on Safe, and the hammer down for double-action-to-single-action operation.
The DA pull is 11 pounds, and the frame affords a lot of grip leverage, so it’s no big deal to operate the trigger quickly in double action. The 0.375-inch-wide grooved trigger shoe was stageable, with take up and a hard stop just before the single-action shot released.
The magazine release is a paddle-style ambi switch located at the rear of the trigger guard.
The Mark 23’s controls are laid out on the left side of the frame and are easy to manipulate. (Woody for TTAG)
HK notes that a pair of Universal Mounting Grooves located on the front of the Mark 23 frame allow for a variety of accessories to be used with the pistol. HK cautions, however, that “Improperly designed or installed accessories may result in damage to the Mark 23 mounting grooves and/or the Mark 23. Such damage is not covered under warranty. Be certain to use only HKI authorized accessories and follow installation and precautions carefully.”
So, to attach standard accessories, you’ll need to have a Picatinny rail adapter, $128. Such adapters are unusual in that they slide onto the frame grooves and screw into the front of the trigger guard, which accommodates specific MK23 accessories such as the Laser Aiming Module (LAM).
The specs say the HK Mark 23 has a “match grade trigger,” but I wouldn’t call it that. The single-action trigger pull is a predictable 6-pound release, and the group testing shows the gun would shoot, so that seems to be nitpickery. But it’s not a 3.5-pound bullseye trigger. For accuracy testing in single action, a round spur-type hammer was easy and positive to pull back.
In the hand, the Mark 23 feels big, and for smaller-handed shooters, the grip will simply be too much to hold well. Some shooters who handled the Mark 23 liked the recoil impulse from the handgun, but the weight tired them out pretty quickly. That weight is even more pronounced with a can attached, but a suppressor makes the Mark 23 a dream to fire.
For this test, I attached a SilencerCo Osprey 45, $734 at SilencerShop.com. According to Silencer Shop’s data, the SilencerCo Osprey 45 provides shooters a hearing-safe 131.3 dB output with subsonic 45 ACP ammo. It has a black-oxide aluminum shell, stainless-steel internals, weighs 11.1 ounces, and is 8 inches long.
I had to buy a new piston for the Osprey to fit the HK. Many .45-caliber pistols (such as FN) have the 0.578×28 tpi muzzle fitment, and a GLOCK 21 is cut to 16mm LH. The HK Mark 23’s thread pitch is 16mm RH, the piston from SilencerShop.com was $71.
The Osprey comes with a three-pronged tool to remove the piston. To install the piston in the end that attaches to the muzzle, the user slides the piston (a stainless cylinder with spokes on one end) into a spring inside a threaded adapter, which then screws into one end of the suppressor.
The HK Mark 23’s thread pitch is 16mm RH. It required a specialized piston for the Osprey suppressor, which was $71 from SilencerShop.com. (Woody for TTAG)
Installation was simple: With the magazine out of the HK and the action locked open, I unscrewed the thread protector, then held the pistol muzzle at 11 o’clock in front of me and started the Osprey onto the muzzle threads. I then screwed the Osprey down as far as it would go onto the muzzle threads, aligned it with the top of the barrel, and tightened the locking lever.
Here’s a suppressed group using Fiocchi 200-grain JHPs. Recovery shot to shot is smooth and easy. (Woody for TTAG)
At 25 yards suppressed, the HK threw Prvi Partizan 185-grain semi-jacketed hollowpoints into groups as small as 1.25 inches. Suppressed, the HK shot 2.1 inches with Fiocchi 200-grain JHPs and 2.6 inches with Winchester white box 230-grain ball. The extra weight of the suppressor really tamed recoil and made cycling back onto targets smooth and easy.
Here’s an unsuppressed group fired in the Mark 23 using Winchester 230-grain ball. (Woody for TTAG)
The big gun didn’t do quite as well without the can, but it was pretty consistent, registering groups of 2.75, 3.0, and 2.8 inches with the same rounds, respectively. Of course, the suppressor-height sights are tall and easy to see, and the front grooves and adapter would have allowed me to attach a laser for even better sighting quality. The sights are three white dots, with two on the rear blade.
The rear sight is adjustable for windage and elevation, and the front post is fixed, rather than being driftable in a dovetail. If I were to buy another Mark 23, I’d plan to add a laser or red dot because, for me, the sights are a limitation on the gun’s accuracy, despite the long sight radius. When I can target with more visual precision, I can shoot the Mark 23 very well.
So, is the Mark 23 worth buying for the regular buyer who’s not Navy SEAL? Yes. It’s one of the best handguns out there, but you’ll pay for the privilege.
If you don’t believe me, read the buyer comments on various retail sites from people who have purchased one. If you already own one or have owned one, please share your experiences with the TTAG readership in the comments section below.
