Hi there, much of my HW100T work has been driven by information from yourself on forums so I do have to thank you. We both have similar issues with this rifle but after a great deal of work I am convinced it is the variable quality HW barrel that lets this rifle down. Some it appears are lucky and get a good barrel and others like myself don’t. From new my rifle had a consistent FPS but produced at very best 1” CTC groups at 40 yards. After hundreds of test pellets with different makes and head diameters I found that JSB Exacts in 4.53 produced the best overall groups. I have measured, rolled, weighed, washed, lubed and sized countless pellets to try and get something close to a more consistently tight group. One thing that confounded me was that it would sometimes achieve pretty much pellet on pellet at 40 yards (all tests rested, nil wind) and then other times would be all over the show. Although I have a polished hammer, different springs, cylinder, AT removed, barrel floating,etc none of this really helped. I did find that muzzle flip can be a cause of inaccuracy if you don’t account for it. Different silencers certainly have an effect and after trying A&M, Qtec and the original Weihrauch I have settled on the original Weihrauch. I also experimented with the Rowan and UK Neil airstrippers but no improvement over the Weihrauch silencer for my setup and shooting at home is easier with less noise. The AA Qtec silencer was quite different to the Weihrauch. I feel this due to barrel harmonics and weight rather than internal design. I use a Hawke Airmax 30 6-24 x 50 and I discovered some of my early accuracy problems were parallax errors shooting on x24. When testing now I shoot x12 or x14. I also went around a pretty big loop on this HW100 two piece action movement/change in POI possibility. I swung from “its definitely poor design” to “its ok, believe in it” with this. I do think the walnut stock doesn’t do the gun any favours. I have a CS800 custom stock and I found it’s important to watch the gap between the top of the cylinder and the bottom of the barrel when you tighten up the back and fore-end screws. If it is not seated right in the stock it will influence the POI however tight the two socket head screws holding the two halves of the action together are. I experimented having the cylinder loose to very tight, it now has a thin rubber washer (bike inner tube) between the cylinder and action to allow some movement due to temperature change and isn’t hard tightened up. (the main inlet valve, cylinder grommet slides in a tube effectively so the cylinder can be safely loose on its thread). Whether this has helped I’m not truly sure. You and others have posted information on measuring shot development time and with Audacity on my PC I have confirmed my sound trace roughly ties with others results. And barrel cleaning - bought a VFG kit and I have figured the best regime for this barrel. Caught fired pellets in water and checked rifling on pellets under microscope. All rifling marks look good and consistent.
Then a new direction when I read your other forum posting titled “HW100 barrel - poor internal finish, lead fouling and accuracy loss”. This prompted me to have a close look at my HW100T crown and lo and behold mine was exactly the same as your problem crown in that excellent picture you put up on that forum. It looks like the crown cutting tool that puts the 60 degree chamfer on had worn and effectively swaged over at the end of the rifling lands. As a quick fix I got someone at work to square the end off of the barrel on a lathe - although I later found out that this had not been done right (more later) this provided a definite improvement. It was also about this time that I discovered that die 34 JSB’s on this squared barrel crown provided very good single hole groups at my 27 yard local indoor range. I bought a sleeve of these from Intershoot but dearly wish I had bought many more sleeves now as nothing else has been as good as these At 40 yards there were signs it was better but there was still this re-occurring issue whereby I would get a few pellets hit pretty much the same hole and then the next shot would be 10mm to the right and then the next shot would be right on top of that. And then it would switch back to the original POI. Very frustrating. So very good but still moving around. Then on a whim I thought new barrel – so I bought a new barrel from Sportwaffen Schneider Germany. This barrel had a very good crown, nice and clean, well cut. It shot good – as good as my original barrel perhaps but the big change was it really favoured lighter pellets for some reason. AA Express and Falcons both did best in this barrel – I got to that point when someone in our local club sent me an article my Steve Pope/V Mach from the April and May 2010 Airgun Shooter magazine (still available by request on the V-Mach website). This talks about the importance of crowning with respect the bore axis. So off the original barrel went to Steve for a professional re-crown. Back on the gun I have not seen any significant improvement but in my own mind the crown is now out of the equation. This is where I am now – still with the original barrel - it still does cloverleaf groups at 40 yards and many shots are pellet on pellet but I still get an occasional bizarrely consistent group to the side.
So if you already think I’m pretty mad having been through all the above my latest mod involves the pellet probe. I read an article from a Dutch 100 yard target shooter (HW100Lightstream on WOC) where he suggested adding 3mm to the length of the pellet probe. So I turned a brass insert up at work and soldered this to the end of another pellet probe. The idea being that the pellet seats itself more fully in the rifling of the barrel at the breech end. Still testing to see whether this has improved anything but results just this last weekend don’t show any big leaps. I also read about this mod in a magazine interview a year or two back with a Field Target shooter but I couldn’t find it again. Anyone ?
Having done all of this I am now perhaps predictably researching the virtues of lapping the barrel. I am in the process of gathering together all the info I can find on this from the internet. “Fire lapping” pellets with a lapping compound syringed in to the breech end seems the easy approach but not very eloquent or controlled. I would also rather start with a minimally invasive approach and build it up. Or perhaps I give up on this and try a BSA or LW barrel. Overall the HW100 is a great design but I do sometimes dwell on the inordinate amount of time I have spent fiddling in order to get it shooting consistently to a standard I know it is capable of !
Last edited by POI; 11th August 2015 at 01:55 PM.