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weihrauch 25mm piston assembly

Discussion in 'Anything Airgun Related' started by martin22, Aug 22, 2014.

  1. martin22

    martin22 Donator

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    can these still be bought new and if so can someone point me in the direction where? or if anyone knows of a second hand one please let me know
    thanks
     
  2. martin22

    martin22 Donator

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    anybody?
     
  3. cloverleaf

    cloverleaf Honorary Member

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    Nope.. they stopped making them in the early-mid '90s (IIRC - I forget exactly when).
     
  4. martin22

    martin22 Donator

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    i thought that was the case,that explains why there like rocking horse **** to get hold of,you would think by now with the 25mm piston being so sought after someone with the engineering tools/skills would be making 25mm piston and sleeve kits to drop in? i think they would prove very popular :cool:
     
  5. Nickg

    Nickg Posting Addict

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    I have been considering a 25mm set up for a project of mine, I intend to insert a tube, ream and hone, Then I use my own rotating piston so the slot isn't important, alternatively a standard piston can be machined down to 25 mm to suit,( not sure if there will be an issue with the cocking link locating in the piston) I have the tube and the ream just haven't got around to it yet.:rolleyes:
     
  6. martin22

    martin22 Donator

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    sounds interesting youll have to let me know how you get on with that,i know bigtoe succesfully sleeved an 80 for a 25mm piston,i think he used a walther lgv piston though,apparantly it shot very sweet indeed
    i also know wonky donky made a rotary piston for the 80 with very good results
    machining a piston down (i presume you mean a 26mm piston?) also sounds interesting but surely that would take too much weight off and ruin the fireing cycle unless you add some weight back to the piston somehow?
     
  7. Jackroadkill

    Jackroadkill Donator

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    They do crop up for sale on forums and Ebay from time to time but they aren't cheap, I'm afraid.
     
  8. cloverleaf

    cloverleaf Honorary Member

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    Sounds interesting; although my gut tells me that the future of 12ftlb springers lies in smaller bore:stroke ratios and lightweight pistons. IME going too short on the stroke reduces efficiency as the duration of the "energy transfer window" is reduced so less energy is transferred to the pellet before the onset of piston bounce.

    I think we need strokes of of 80-90mm but with reduced bore diameters - would be interested to see how rifles with 22 or 20mm bores would fare in terms of overall output, efficiency and firing manners..
     
  9. martin22

    martin22 Donator

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    ill happily pay good money for one jr,just need one for my next project :up:
     
  10. Jackroadkill

    Jackroadkill Donator

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    I'll let you know if I see any that are for sale then, Martin.
     
  11. martin22

    martin22 Donator

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    thanks jr :thumb:
     
  12. Nickg

    Nickg Posting Addict

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    I have done my own rotating piston 97 with a 26mm piston, The pistons I make are about two thirds the weight of the standard one , and shoot very well so I know the piston weight won't be a problem.
    But I feel 25mm will be even better, so my project involves sleeving down to 25mm, going to have a go this afternoon so we shall see.
     
  13. Nickg

    Nickg Posting Addict

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    I have had a success with my 25mm comp tube conversion, I used a piece of hydraulic tubing, which I bored and reamed to 25mm( no mean feat as the wall thickness is now only .5mm).I then honed and polished the bore to a very good finish and Loctited it into the 26mm Comp tube. Need to let the Loctite set now so I can machine the waste of, and drill the cocking slot in.

    View attachment 102458 View attachment 102457 View attachment 102459
     
  14. Nickg

    Nickg Posting Addict

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    Ok Finished the comp tube this morning, and it holds air so it will be going into my project 77 , here is a pic of it finished with one of my own seals :)

    View attachment 102491
     
  15. Jackroadkill

    Jackroadkill Donator

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    Purely out of interest Nick, what advantages do your seals give over the factory ones?
     
  16. Nickg

    Nickg Posting Addict

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    I am experimenting with these and have them in four peoples guns including my own. I find the o ring seals more effectively and gives a faster shot cycle, while the polyurethane head gives a softer shot feel.
    A friend has one that also gives a shorter stroke in his,97 , he used to call the gun THUMPER, not any more, the shot cycle is faster, smoother, and there was an increase of 30 fps over the standard set up, a big difference for a small modification. Vobster was the first to try one, and he reported a good improvement, be nice to know how it is performing a bit further down the line.
     
  17. martin22

    martin22 Donator

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    looking great nick,can only imagine how popular a 25mm conversion kit would be for the 77/97 or most other hw's infact :cool:
     
    Last edited: Aug 25, 2014

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