H&K Squad Automatic Weapons: The Story of the HK23

Look, the HK23 isn’t just another machine gun that came and went. It’s actually a pretty fascinating look at how weapons evolve when engineers have to deal with real-world military requirements that keep changing on them. Heckler & Koch built this thing trying to crack the US Army’s Squad Automatic Weapon program, and the whole saga is kind of a masterclass in adaptation. You’ve got the HK23, then the HK23E, the HK13, and honestly, each version tells you something about what happens when theory meets battlefield reality.

Where It All Started

So the 1970s roll around, and the US Army decides they need something new. They’re running this Squad Automatic Weapon (SAW) program, trying to get squads a lightweight support weapon that could actually lay down sustained fire without weighing a ton. The thinking was pretty straightforward: ditch the heavy 7.62mm systems everyone was lugging around and go lighter with 5.56mm. Makes sense, right? Less weight, easier to carry, and you can still put rounds downrange when you need to.

Here’s where it gets specific, though. The Army wasn’t messing around with vague requirements. They wanted a weapon that weighed no more than 9.07 kg (20 lbs) when fully loaded with 200 rounds. That’s actually pretty demanding when you think about it. You need something one person can carry and use effectively in all kinds of situations, and it can’t turn into a boat anchor.

H&K Takes a Swing

Heckler & Koch already had a reputation by this point. They knew their way around innovative firearms, and they saw the SAW program as a chance to get into a new market. Initially, they looked at the HK21, this machine gun they’d built using their roller-delayed blowback system. The HK21 was solid, reliable, good firepower. Problem? It weighed 11 kilograms (24 lbs). Nowhere close to what the Army wanted.

So the engineers in Oberndorf went back to the drawing board. They took the HK21’s basic concept and started figuring out how to shed weight without losing what made it work. What they came up with was the HK23, a belt-fed light machine gun chambered in 5.56x45mm NATO.

Unloaded, the HK23 hit 8.5 kilograms (18.7 lbs). That’s way lighter than the HK21. But here’s the thing: when you add the ammunition, you’re still over the limit. Not by a ton, but enough to be disqualified. Bit of a letdown, honestly. Still, the HK23 showed that H&K could take an existing design and reshape it for new needs. That ability to iterate would become pretty important as the story continued.

The Basic HK23

The HK23 was a real shift from the heavier HK21, but it kept the core design philosophy H&K was known for. Chambered for 5.56x45mm NATO, which by then was becoming the standard NATO round. Lower recoil, lighter ammo, plays nice with other weapons in the inventory. The whole point was making something portable enough for squad use while still being able to throw lead when things got serious.

What Made It Tick

The shoulder stock came from the HK11, made of tough plastic. Kept the weight down without compromising strength. The pistol grip had this thumb rest and finger grooves, clearly designed for right-handed shooters. Not ideal if you’re left-handed, but that would get addressed later.

For feeding, they went with a fixed belt feed mechanism. Simpler design, less to go wrong, and it could handle 200-round belts loaded into external ammo boxes. Pretty standard setup for sustained fire.

Sighting was interesting. They used a drum sight that adjusted for height and windage, with a 590 mm sighting line. Not the longest out there, but decent for medium-range work.

But yeah, the weight thing kept being an issue. Loaded up, you’re looking at over 10 kilograms (22 lbs), which meant the Army wasn’t going to bite. Back to the workshop.

The A1 Version Shows Up

The HK23A1 was H&K’s response to the Army revising their requirements. Funny enough, the Department of the Army bumped up the maximum weight to 9.5 kg (20.9 lbs). Suddenly there was a bit more room to work with.

What Changed

The stock got reworked. Now it had a clip-on plastic cap and an integrated buffer baseplate, which helped with recoil management. If you’re going to be firing this thing in bursts or on full auto, you want it to settle down between shots.

The belt feed system became modular, which was a smart move. You could fold it down to make loading easier, or swap it out entirely for a magazine adapter. Operators could run loose belts or use belt boxes, depending on what made sense for the situation. More flexibility in the field is always good.

They also changed how everything fit together. The grip, housing, and stock now used locking bolts, making disassembly and reassembly way more straightforward. Less time fumbling with components during maintenance.

Testing Didn’t Go Great

Aberdeen Proving Ground got ahold of the HK23A1 for trials, and things went sideways. The testers were using experimental XM287 ball ammunition and XM288 tracers, which weren’t actually compatible with the weapon. On top of that, improper handling during disassembly and reassembly caused performance problems. You can build a great weapon, but if the test conditions are off, the results won’t reflect reality. H&K took notes and kept refining.

Enter the E Models

By the early 1980s, H&K had learned enough to produce the HK23E and HK23E1. These versions incorporated all the feedback from earlier trials and pushed the design further.

Major Upgrades

They extended the housing, which bumped the sighting line up to 685 mm. That extra length meant better accuracy at distance, which matters when you’re trying to support a squad at medium to long range.

Here’s something you don’t see every day: ambidextrous controls. The fire selector lever now worked for left-handed shooters too. Small change, huge impact if you’re one of the people it affects. The selector kept the usual modes: single shots, three-round bursts, and full auto.

Ammunition Tweaks

The E and E1 models had different barrel twist rates to match specific ammunition:

• HK23E: 178 mm twist for SS109 and L110 NATO-standard rounds
• HK23E1: 305 mm twist for M193 and M196 ammunition

It’s one of those details that seems minor until you realize how much it affects performance. Different ammo needs different stabilization, and H&K was making sure the weapon worked optimally with whatever you fed it.

They also threw in extras like a silent closing slider, integrated cleaning equipment, and compatibility with scopes via STANAG 2324 rails. Practical stuff that makes life easier in the field.

The HK13 Takes a Different Path

While all this was happening with the HK23, H&K’s engineers were also working on the HK13. Think of it as the HK23’s lighter, more agile sibling. Magazine-fed instead of belt-fed, built for portability.

What Made It Different

The HK13 was about 5 kilograms lighter than the HK23. Five kilograms. That’s a massive difference when you’re humping gear around. Made it perfect for situations where you need to move fast and can’t afford to be weighed down.

Instead of belts, it used standard 30-round magazines. Simpler logistics, quicker reloads. You’re not dealing with belt boxes or loose belts, just magazines you can swap out in seconds.

It still had the good stuff: quick-change barrel grip, adjustable bipod, roller-delayed blowback system. Reliable and accurate across different firing modes. And because it shared components with the HK23, you could maintain both weapons with the same parts and tools. Smart thinking.

What It All Means

The HK23 series is basically a study in how you iterate your way to better firearms. The US Army’s SAW program kicked it off, and each version of the HK23 addressed problems that showed up during testing. Weight issues, feeding mechanisms, ambidextrous controls, ammunition compatibility. H&K kept refining until they got it right.

That roller-delayed blowback system? That’s pure H&K. They built their reputation on it, and the HK23 series shows why. Reliable, precise, and adaptable to different configurations.

The HK13 and the other variants show H&K wasn’t just focused on one approach. They understood different units have different needs. Some want belt-fed sustained fire, others need magazine-fed mobility. H&K tried to cover both bases while keeping performance high.

Looking Back

You know what’s interesting about the HK23’s legacy? It’s not just about the technical specs or meeting military requirements. It’s about how you take feedback and actually use it. How you adapt when your first attempt doesn’t quite hit the mark. How you build weapons that work in the real world, not just on paper.

The HK23 series influenced how people think about squad-level weapons. The innovations in weight reduction, modular feeding systems, and user-centric design became reference points for other manufacturers. Even the parallel development of weapons like the HK13 showed you could diversify offerings while maintaining engineering standards.

Heckler & Koch’s approach with the HK23 was iterative and responsive. They didn’t get it perfect on the first try, but they kept refining until they had weapons that balanced firepower, precision, and practical usability. That’s harder than it sounds.

These weapons mattered not because they won some massive contract (they didn’t), but because they showed what’s possible when you combine engineering excellence with genuine attention to operator needs. The HK23 series proved that innovation in firearms isn’t about revolutionary leaps. Sometimes it’s about taking solid foundations and making them better, one iteration at a time.

And honestly? That’s probably the most important lesson here. Build something good, listen to feedback, make it better. Repeat until you get it right. The HK23 may not be as famous as some other H&K weapons, but it deserves recognition for pushing squad automatic weapon design forward during a critical period in small arms development.