Nobody seems to have addressed the question.
I have an HW80K and I love it. In my opinion, the following is all you need to do:-
1) dismantle (see YouTube). The trigger block may need a hell of a whack to start it turning on the thread, then when it approaches the end of its travel, brace hard against something for the last turn or two - just in case.
2) clean spring, interior of compression chamber, piston, everything. Get the grease gunge OFF. Including the trigger. Just wipe it - enough will stay on to provide lubrication for years.
3) de-burr (smooth off the inside edges) of the slots in the compression chamber - use wet and dry paper
4) Source/buy a tight fitting spring guide and a top hat (failing both, the top hat only and retain the original spring guide)
5) - this is optional but a good thing to do - fit a piston 'short stroke extension'. Tinbum Tuning do one at modest cost. Alternatively, don't bother.
6) Re-use the original Weihrauch spring. Virtually every other replacement (excepting probably V-Mach) is highly likely to take the rifle above the legal limit, especially the Titan mainsprings, as their recommended springs for any model puts them firmly well into FAC territory, unless you shorten them. The Weihrauch springs are GREAT.
7) lubricate everything INSIDE the piston (spring, spring guide, top hat surfaces) with sparingly applied Molybdenum Sulphide grease (Halfords). Put the thinnest smearing of same on the exterior of the piston. Lubricate the (clean) piston seal around the edge with a really fine film of fully synthetic car engine oil. Take care to get NO lubricant on the front of the (clean) piston seal.
😎 Re-assemble and enjoy. If you have added a short stroke extension it will have effectively increased the spring preload as well as reducing the swept compression volume, so be prepared to have to tension the spring harder to start the trigger block in its retaining thread. The combination of the reduced swept volume and the increased preload will put things pretty much back where they were, power wise. My experience tells me that overall, probably the most vital component you can add is the top hat. That, combined with a tighter spring guide, will alone change the shooting experience.
I recommend that you check the velocity of the pellets fired - try several different weights - to confirm that the rifle remains below the UK legal maximum ft.lbs. output. You will also be able to check how consistently the rifle is now shooting from the fps speed over several shots.
I have 'short-stroked' HW95s and HW80s. My conclusion is that the larger diameter, longer compression stroke of the HW80 benefits from doing so, whereas the smaller diameter, shorter compression stroke of the HW95 does not. I also believe any break-barrel Weihrauch works better in .22 calibre than in .177.
Doing the above will teach you about the rifle and show you what is important to make it function at its best. It will save you heaps of money by not falling for 'black art' tuning companies - and your rifle will shoot very nicely indeed.
