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After all the interest in the Brno ZKK pop up peep sights, I thought I'd share a recent ZKK600 makeover project.

I had bought a cheap ZKK 600 in .270 Win (pop-up peep and the Zeiss Jena 6x32 scope!) with the view to rebarrelling to 9.3x62mm… but unexpectedly came across a mint Sako AV in that calibre, which I snapped up fast instead!

This left me with a spare ZKK600, so I after a quick crown job (ZKK's are always poor) I took it down to the range and put a packet of Remington 130gr factory loads though it to see how it performed. Although the barrel has some light pitting here and there, a good clean with Sweets and a treatment with JB paste had a best group of 5 shots into ~30mm… good enough for a hunting rifle out to 200m… so a keeper!

Since the rifle hadn't cost me too much I thought I'd see how far I could go just by reblueing the metal and reworking the stock.

One reason why late model ZKK's had problems with wandering a zero is that the 'rosewood tip' is actually part of the stock and just stained while the white line spacer is actually a U shape inletted into the fore end via a cut that nearly goes right through the timber!

There is a small ramp in the barrel channel which is supposed to give some upwards pressure to the barrel, but as the spacer is glued into the stock, over time the glue fails and the entire fore end tip is free to flex wherever it likes. I sawed the rest of the way through the factory tip then dowelled and fitted a proper contrasting fore end tip. A standard grip cap from Brownells replaced the rather gaudy 'rosewood' grip cap, and blued to match the barrel.

Existing checkering recut:

I unsoldered the original barrel band foresight ramp and fitted a Recknagel QD barrel band, cleaned up the barrel and re-attached the foresight after cleaning up the profile with small files and wet and dry paper down to 400 grit.

I then turned my attention to cleaning up the receiver and bolt…
Feedramps were cleaned up with a Dremel, then polished.
The receiver rails were stoned smooth, then lapped into the bolt body using fine valve grinding paste, the end result was very smooth travel indeed.

Many ZKK's suffered from poor quality surfaces esp around the LHS lightening cuts after factory cutting with poorly maintained profiling tools… this took a lot of time and effort with diamond files and stoning but was worth it!

The ejector plate was removed and small burrs cleaned off to slick up the travel (again worth checking for burrs as this can cause inconsistent ejection). The receiver was then masked and bead blasted to match the factory finish. The bolt was then stripped (using the nifty disassembly tool supplied with every rifle) cleaned and polished, again down to 400 grit.

The trigger guard and magazine floor plate had some quite deep scores and took a lot of time to clean up.

The trigger pull adjuster set screw was found to be stripped, so the thread was cleaned up with a button die, with the corresponding hole in the receiver retapped.

This screw is often found to be stripped on ZKK's as the unsuspecting owner tries to adjust the terribly creepy standard trigger pull.

If adjusted too far in it drops out of the threaded hole, but spring pressure makes it cant over… if the screw is reversed carelessly, it will start in the threads offcentre and then strip and bind halfway up as the hapless owner cranks on the screwdriver.

I'm not a fan of the ZKK set trigger, it can be adjusted and stoned to give a good release when set… but is always dreadfully vague and creepy when used unset.

It is also rather noisy… the sharp CLICK when setting will alert game.
Just replacing the set trigger with the standard trigger won't improve things much either… the pivot pin need to be replaced with a larger diameter one to remove axial play (I just measure the diameter of the standard pivot pin with a micrometer, then use an imperial, or a number/letter drill cutoff at the shank to give a slightly tighter fractional fit) the standard sear engagement is usually around 1.5mm… WAY too much, so it needs to be carefully ground back , then all surfaces stoned for a crisp release of ~3lb.

The safety has a rubber buffer block, which gradually dissolves (under the influence of 30+years of oils or solvents) into black goo that spreads though the safety recess and then hardens. This always needs to be checked on any second hand ZKK, as it can cause the safety to not engage correctly.

Anyway… it was an interesting and satisfying project.. hope you enjoy the results!