The original barrel for the K1 was made by Lothar Walther. It was/is a top quality barrel, which could shoot pellets very well.

However, given the particularity of the K1's design and the fact that it shoots straight from the magazine (which acts as the chamber), this meant that by using a more “generic” barrel (i.e. not specifically designed for the K1), it required some experimentation with several pellets/slugs to finally find the ones that worked well with it.

Once the correct ammunition was identified, the K1 with the Lothar Walther barrel was a dream to shoot. However, it remained somewhat pellet picky. With slugs, Huben developed their own dedicated slugs for the K1, which performed very well with the Lothar Walther barrel.

Broadly speaking, there are two K1 versions: the early one produced until early 2020, and the later “post-2020” version. While these names are not official, referring to them as MK1 and MK2 is acceptable when distinguishing between the two.

The major change introduced in 2020 is the barrel: an unchoked barrel designed to fit perfectly with the K1 firing directly from the magazine, and able to shoot accurately both pellets and slugs.

The latest K1 also performs very well at any power level, while the original version performed considerably better at higher power levels.

Huben continuously improves quality control and incorporates customer feedback, so minor variations may exist between production batches. Other labels used online are unofficial and typically reflect only small, incremental changes rather than major differences in parts or functionality.

Both the Standard and the Special Edition share the same platform at their core. All internals, barrel, reservoir and gauges are the same, and performance should be identical.

The main differences are external. The Special Edition comes with a high-quality wooden stock instead of the synthetic one, and both the stock and the shroud are made of carbon fibre.

These elements make the Special Edition slightly lighter overall. The shroud vents are also positioned towards the back, closer to the shooter, which may make it feel louder to the user, but from the front of the airgun it is quieter.

Note: late Standard Edition models also have rear-positioned vents.

Being hammerless means that the trigger acts directly on the sear of the valve with no hammer strike. The valve, driven by a piston, is immediately opened by the pressure of the plenum.

Not needing a hammer to overcome the resistance of the valve means fewer moving parts, fewer vibrations (which can impact accuracy), higher efficiency, and more power.

Accuracy, power and reliability are the direct benefits of this unique action which Huben pioneered.

Yes. While shooting straight from the magazine could present some challenges, the latest K1 handles it very well. As with any rifle, slugs may require some testing to find what works best with your particular airgun.

If you do not have time to test many slugs, we can narrow it down to options we know work:

• .22 calibre: Zan .219 (22 and 28 grains) and EDgun/JSB KnockOut Slugs MKII (.216)
• .25 calibre: Zan .253 (33 and 38 grains) and EDgun/JSB KnockOut Slugs MKII (.250)

Yes. Power is adjusted via a screw accessed through the grip.

Turning it anti-clockwise increases power, while turning it clockwise reduces it. Power output also depends on fill pressure, with higher pressure resulting in higher power.

Do not allow pressure to drop below 150–160 bar (180 bar with heavier ammunition).

Power should be adjusted gradually and ideally with a chronograph.

The adjustment screw has no physical stop and should not be unscrewed fully.

The recommended maximum is two full turns (720°), or up to two and a half turns only if refilling at 220 bar.

Yes.

Use correct slug diameters: at least .219 for .22 calibre and .253–.254 for .25 calibre.

The original GK1 is unregulated.

With manufacturer approval, Wolfiek Group developed a regulated version featuring an internal regulator and a K1-style filling port with an integrated gauge.

Yes. Power adjustment works the same way as on the unregulated version.

The regulator pressure should not be adjusted, as it is factory-set to the optimal level.

The regulated version offers increased consistency and efficiency, with near-identical power from the first shot to refill.

It also allows the pistol to be tuned down to sub-6 ft-lb, which is not possible on the original GK1 V3 at full pressure.