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Thread: HW50 mods and bedding

  1. #1
    Sharp Shooter

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    Default HW50 mods and bedding

    After almost 5000 shots I decided it was time for a few little tweaks and modifications. I did not have a camera at hand, which is why the explanation is a little long-winded...

    First up was the trigger. I have been shooting mostly offhand at silhouettes lately, and even with the pull set as light as possible, the second stage was still a little gritty and required more force to squeeze off than what I could manage without yanking the sights off-target.

    I took the trigger apart one piece at a time, polishing contact areas to a mirror-finish. The u-section of the lower sear had worn two deep grooves where the trigger pins make contact, and I had to remove quite a bit of material before they were polished out.

    One other thing I wanted to sort out with the trigger is the tendency for the first stage to lose spring tension after it is taken up for the first time. My guess would be that the friction between the sears is too great for the spring to overcome and the sears remain "stuck" at the end of the first stage. This then leaves the trigger blade completely floppy until second stage is taken up.
    I then polished the culprit sear contacts and while testing the trigger on its own, it seemed to work. I could clearly see the sears reset after releasing the first stage. However, when I finally put everything back on the rifle for a test shot, the problem was back.
    I think that the sharp edge that I left on the sear (it picked up a curly when I pulled it across my fingernail like some micro block-plane!) digs into the opposing sear, preventing it from sliding in one direction.

    The second stage is much better now and I was able to shoot a few 10mm groups at 12m for the first time. Not great, I know, but not too bad for shooting offhand and with open sights either!

    Next up was the cocking-link, another u-channel member that was digging trenches into the bottom of the receiver tube. It has a little slider wheel that is sitting too low in the channel to prevent the flanges from also making contact. The wheel is a loose fit on its pin but does not turn easily.

    Having designed an aircraft wing spar from ali and earning some hard-won buckling experience (believe me, it was not pretty!), I judged this link to be a complete over-design and promptly ground away about 1mm from each flange. This ensured proper clearance all around, but that shoddy wheel still caused undue friction while cocking.
    I then cut a stub of 8mm brass tube, slit it and fit it around the wheel. I wedged the bottom of the wheel, preventing it from turning so that the brass can slide. The effect was instant improvement, but the brass soon worked off the wheel and I was not ready to start gluing things in place just jet. I had one more solution to try - a half-moon shaped nylon block that fits over the wheel. Even better that the brass, as it turned out, smoother to cock and less effort required. So it will stay until it is worn through at which time I will replace it with Delrin or Vesconite.

    I left the biggie for last - bedding the action. I read Blud's how-to in the technical reference section. It seemed like a horrible job but worth the effort. I must have changed my mind a dozen times between bedding the entire action with epoxy and cotton flocks, and only bedding a few select areas using pratley putty (the easier, less messy option).

    I finally convinced myself, with Blud's encouragement, that if it is worth doing, it is worth doing properly. I started with wrapping the action in glad-wrap, but soon changed my mind and painstakingly mummified the action in masking-tape, but leaving as much bare metal as possible for a true mated fit.

    I then rubbed some neutral kiwi shoe-polish on tape and metal as a release agent and got to work on the stock to prepare the mating surfaces. This basically involved scraping off any varnish with a course half-round wood file, leaving nice deep grooves for the epoxy to grip. Any adjacent areas on the stock that might get some epoxy on it once it starts to squeeze out was also covered in masking tape.

    I had some left-over epoxy from a kayak project (AMT SP106) and mixed up about 25ml. I dabbed all the bedding areas on the stock with clean epoxy first, since the low viscosity will give proper penetration into the wood. I then added cotton flocks and wood flour to the remainder and applied the paste to the stock. I added a little more flocks for a firmer paste in areas where large gaps need to be filled, such as the gap right at the rear of the receiver.

    The epoxy is curing as I am typing, so tomorrow will be the day of revelation! I will try and remember the camera for the remainder...
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  2. #2
    REP: Oom A's Airguns

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    Good post William.
    Remember that when the rifle is cocked you have the pressure of the main spring being exerted on the sears. A 5.5 to 6 FPE might reset the first stage but I have yet to find a 12 FPE and higher springer that fully resets the first stage.
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  3. #3
    Sharp Shooter

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    Quote Originally Posted by Adrianv View Post
    Good post William.
    Remember that when the rifle is cocked you have the pressure of the main spring being exerted on the sears. A 5.5 to 6 FPE might reset the first stage but I have yet to find a 12 FPE and higher springer that fully resets the first stage.
    On which of the sears on your 77 did you change the angle?
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  4. #4
    REP: Oom A's Airguns

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    The sear that engages the piston rod. It was changed for me. I have never compared it to a standard one to see the difference.
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  5. #5
    Sharp Shooter

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    Nice post, and a great pity that there are no photos
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  6. #6
    Inactive Member

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    Yes we need fodies
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  7. #7
    Sharp Shooter

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    f you have trigger issues I have found that the BAM B-26 or RWS 320 Rekord trigger copies are near exact copies and you can use their parts or the whole unit in a Weirauch, I (read MZE) fitted an origional Weirauch trigger and it works perfectly.

    Also when fitting that trigger blade, first clean off the rolling pins on the top with alcohol or something and then give it a little spot of, prefferably, silicon grease.
    Makes quite a difference.

    On that many shots, contact MZE he has quite a few Weirauch springs lying around from Vglide conversions.
    Could be worth it too replace that, unfortunately because it has the centre release mechanism of the trigger on the piston you cannot gas ram it.
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  8. #8
    Sharp Shooter

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    Quote Originally Posted by Capt. Oblivious View Post
    Yes we need fodies
    Do we have to explain everything to you in pictures?
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  9. #9
    Sharp Shooter

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    Yes yes yes, photos please
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  10. #10
    Sharp Shooter

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    The good news is that Bad News is once again shooting a snotskoot!

    Since I had to do a proper strip-down to clean up all the shoe polish I was able to also get pics of some of yesterday's mods.

    This morning before pulling the action apart: (trying photobucket for the first time, hope I copied the correct link!)



    The slider wheel with the brass clip (badly warped) and the nylon shoe:



    Some more pics before and after separation:





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  11. #11
    Sharp Shooter

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    Taking the stock and receiver apart only took a rap from a screwdriver handle and a firm pull.

    The epoxy pics up the finest detail, such as the edges of those 4 square inserts above the trigger. The shoe-polish did a good job of preventing any epoxy from seeping in around the inserts.

    Cleaning up all the squeezed out epoxy was tedious, and even though I was in no rush I still nicked the stock in the process, especially along the straight edges running along the receiver.

    Now if you'll excuse me I've got some more shooting to do...
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  12. #12
    Sharp Shooter

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    Thanks William, very nice write-up.
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  13. #13
    Sharp Shooter

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    I started this thread not knowing if it was going to turn out as a "How-to" or a "How-the-hell-NOT-to", but reasoned that either way it will be useful, if only as a warning to others!

    The shooting feels a little different - not as much as I was expecting based on what I read other people experience after bedding their rifles. But then maybe it's just me...

    The most notable change is that Bad News likes JSB's again! Those H&N FTT's were starting to bankrupt me, plus I still have 3 tins of JSB pellets left over from a few months ago.

    I hope some expert can point out, based on the pics, what I did right and wrong. For future reference.

    I am still, for instance, not sure if I should also bed the front screw attachment point?
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  14. #14
    Sharp Shooter

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    After the recent spring failure (see https://www.airrifle.co.za/showthread.php?t=29528 ) I took the opportunity for some further tinkering.

    I got it back from Kevin today after he fitted a new spring (Gecado). The piston liner was replaced with a plastic tube that is thick enough to also act as a front spring guide. Since there is no contact between the spring and any other metal, it was installed completely dry, with not a hint of buzzing.

    He also added a radius to the inner edge of the transfer port and flared it towards the outside like a de Laval nozzle. We were hoping to also experiment with a new piston seal but the material available at the time refused to be machined as desired, so a standard Weihrauch seal was fitted.

    Lastly he modified one of his Airvolution silencers to slide 2/3rds of the way beyond the muzzle and made a cutout for the front sight tube. There are still some small gaps around the front sight that needs to be sealed off properly, but there is already a marked decrease in noise - at least the wife thinks so!

    The recoil (what little there is) has a distinct torsional component that I want to get rid of, so the rifle is coming apart again soon so that I can polish the ends of the spring. Will take some pics of the details then.

    I have no idea how the new spring compares to the original HW part, and it is hard to tell if it is shooting harder or not, so a chrony session should satisfy some curiosity. It will unfortunately be hard to tell how much difference, if any, is due to the new nozzle shape and how much due to the spring.
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  15. #15
    Sharp Shooter

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    Interesting, after reading up about transfer ports on airrifles, I came to the conclusion that straight is used for a reason, however I had a niggling feeling that a rocket style nozzle should be better (once you've redesigned EVERYTHING to work with that parameter) Because it is built to take pressure and make velocity in huge qty's... Except I wondered about making the piston side cone, much flatter to not decrease compression ratio too much. Cool development. Looking forward to it...
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