Can't crack 800fps..

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  • Can't crack 800fps..

    Hey guys,

    Well been playing with the '80 for a while now and have come to the conclusion that she won't crack 800fps. Not fussed but I thought it might've with the latest tune..
    The latest tune included honing the cylinder, reaming out the transfer port to 3.5mm, fitted a new Vortek kit (but retained the V-Mach piston washer), new breech seal, chopping the barrel to 16" and re-lubing. The only one last thing is replacing the piston washer with a new standard one so then all the internals are brand new.

    Using H&N FTT 14.66gn pellets it has a MV of 760fps and a ME of 19.4 ft/lbs. Surprsingly, it only shoots the 13.4 JSB's only 15fps faster... thought being 10% lighter that go a fair bit quicker but there you go. Steve Pope told me that shortening the barrel will probably cost me 10-20 fps which once again, I'm not fussed about. With the longer barrel, she would've got pretty close.

    19ft/lbs is pretty good, but that what Weihrauch claim for a standard twangy unaltered factory 80. Which leads me to think that maybe Mr Weihrauch's pants are on fire when stating MV's of standard rifles... or I've just got a slow gun?

    Has anyone chrono'd a standard '80 or '97 and if so, how close were they to the claimed MV. I'm now thinking that it'd be a bit under what they claim... but, hey, all air-rifles seem to do that now... or they chrono them using those stupid tin pellets!

    GB,

    Russ.
    __________________
    "A gun is like a parachute..
    If you NEED one, and don't have one,
    you'll probably never need one again!"

    You'll probably never NEED a gun. In fact I hope you never do. BUT IF you do, you will probably need it worse than anything you've ever needed before in your life...

  • #2
    Just thinking how funny it is I was chasing 2-3 ft/lbs for my '80, when the difference between the starting to maximum loads in my .458WM is over 1000ft/lbs! 4000-5200!
    __________________
    "A gun is like a parachute..
    If you NEED one, and don't have one,
    you'll probably never need one again!"

    You'll probably never NEED a gun. In fact I hope you never do. BUT IF you do, you will probably need it worse than anything you've ever needed before in your life...

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    • #3
      Get a .204 Ruger...up to 4000' per second.
      I'm in love with Jennifer Hawkins and Alessandra Ambrosio

      Comment


      • #4
        It's not my own personal testing but hope it provides some insight. Done with .177 not the .22 I think you're using Russ, should be the same gun with a different barrel.
        Chrony results at 3:40.

        http://m.youtube.com/watch?v=_4ZDVKuZOsk

        Chewy.

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        • #5
          One more thing...what is that "Lifters For Christ" thing all about on your avatar.....weird.
          I'm in love with Jennifer Hawkins and Alessandra Ambrosio

          Comment


          • #6
            Hello Russ. I've lost the chrono records, but when I put a V-Mach kit in my 80 a couple of years ago it went from a twangy 17ish fpe to a nice crisp 19 fpe with FT&T, so pretty similar to your experience. After only about 50 shots it was giving 20 fpe. Can't tell you what happened after that because I sold it (seemed like a good idea at the time ).

            That was with a full-length barrel, one "power washer", and no internal modification other than a bit of a polish on the piston skirt. I've no idea how it compared with factory specs because (as we all know) factory specs are designed to sell you stuff, not tell you stuff.

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            • grmkc
              grmkc commented
              Editing a comment
              Russ,

              My calculations for your FTTs 14.66g & 760 fps give 18.81 fpe and JSB 13.4g & 775 fps give 17.88 fpe.
              If we did a rough calculation with Exact Jumbo Heavies of 18.13g and say 720 fps, we get 20.87 fpe. At 750 fps we get 22.5 fpe. :S

              I was under the impression you were chasing power. Defined as kinetic energy and in the imperial measurements, the fpe value. The calculation is such that both the weight of the pellet and the speed have an influence, the major contribution is from the weight due to the value being squared. KE=0.5mv2. Where m is in kg and v in m/s. There's a conversion factor to the old imperial fpe which is a constant and doesn't change. (Edited GRMKC 17:25pm) Sorry Paul, the scientist in me missed that little bit but crucial bit.

              So Russ, lets take a step back. Speed or Power?

              It's also difficult to tie the changes in velocity for your rifle down to any single change as you made several changes over a short time with no settle in period in between. For example my HW95. From the time we had that shooting meet, my HW95 has gone up 30 fps with the same FTT head size just from the bits bedding in. You've had several major rebuilds over a short period with no real settling period.

              Geoff

          • #7
            Try it with heavier pellets if you really want to crack 20 fpe.

            It's a bit academic really between 18 & 20 fpe if the gun shoots accurately (the quarry won't be able to tell the difference that's for sure ).

            Matt W

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