Preferred muzzle energy/pellet speed

Discussion in 'Piston & Spring' started by Cooper_dan, Jul 3, 2018.

  1. Cooper_dan

    Cooper_dan Well-Known Member

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    For the last year I've been convinced that 760 - 770 was the magic number for my TX with JSB Exacts, but now I'm not so sure.

    Last week I fit a new spring and seal to the TX. Shot 200 ish pellets through it till the power rise seemed to slow down/stop, then had a washer out. That left it on 740 fps (10.25 ft-lb). Decided to leave it there for a couple of weeks to see if the power would change any more.

    At the weekend I went out with my 'underpowered' TX and got my PB on Saturday (54) then matched it on Sunday. Had a bit of time at the range and accuracy is the best it's ever been.

    Could this purely be down to less power = less recoil and easier to shoot. Or is this die of Exacts possibly more stable at this lower than usual speed? Would be interested to see what pellet speed other people have found works best in their springers.
     
  2. RobF

    RobF Administrator Staff Member

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    Less power feels better in springers.

    A lot of the exotic tunes had people singing their praises for feel, and while some of that wa down to the tune it was also down to the fact that at 10 ft-lb springers feel good anyway.

    If you start chasing the power, especially with less efficient pellets like express they feel harsher no matter what.

    The windage advantage of the speed is much smaller than many think and I find you gain more than you lose by catching sight of your pellet hitting which is easier with lower power.
     
  3. Alanok2002

    Alanok2002 Active Member

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    I thought express were more efficient
     
  4. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Every day's a school day ;)
     
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  5. biwain

    biwain Tree bark and paint chipper Champion

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    We all agree!!!!!!!!
     
  6. custompaint

    custompaint Optics Warehouse

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    mine is running around the 745-755 fps with 8.4 jsb, depending on weather
     
  7. hmangphilly

    hmangphilly Can't Re Member

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    interesting
     
  8. Nomads HFT

    Nomads HFT Well-Known Member

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    In reducing muzzle energy, you've reduced the piston displacement during the compression stroke, giving a very small reduction in recoil. At piston bounce, you've lowered cylinder air pressure, giving less force to drive surge, albeit against lower force from the reduced spring preload. The shot cycle will feel better.

    It's possible that you have moved the pellet exit away from a node and toward an antinode in first mode barrel vibration, which will tighten groups.

    Maybe on Saturday your lowered expectations made you more relaxed, possibly aiding your PB, and on Sunday your consequent increased confidence helped.

    I doubt that external ballistics played as great a part.
     
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  9. Airlexx

    Airlexx Member

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    Dare I say that i’ve come to the same conclusion....

    Had my springers set up at 240 m/s 787 ft but by accident found ot that when shooting at lower speeds it was way less difficult!

    I started this all with the pcp match rifle of my 8 year old, that goes as fast as 203 m/s with JSB exact wich ominously comes out to 666 ft and even in windy conditions performed great.....

    So now i start to let go of the close to 11.99 ftp and my springer now does 206 m/s with exacts and 226 with express and shoots great!
     
  10. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    My TX is running a little lower than I usually run it at the moment. It's doing around 735 fps with Exacts which is a little over 10 fpe.

    Thinking about it, all of my best performances have been when my gun is doing less than 750 fps with 8.4's.

    I don't know why, could be a number of things including coincidence.
     
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  11. Cooper_dan

    Cooper_dan Well-Known Member

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    Jim, I daresay you are absolutely correct with regards to the lower expectation/higher confidence. It's very difficult to say whats happening in this kind of scenario where the shooter is always the most variable factor. Saturday and Sunday I got up early and did my rowing/stretches so better preparation might have helped too.
    Hopefully this renewed confidence will stretch as far as the next Nomad's shoot :D One thing is for sure. I won't be messing with it anymore!

    Airlexx, 206 m/s is very low but I can image the rifle feels amazing at that power! I do have a spare TX for just this kind of test....

    Brian. I hope it isn't coincidence, but you might be right, combined with what Jim mentioned.
     
  12. Nomads HFT

    Nomads HFT Well-Known Member

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    Another thought, Dan. I don't have hard data to back this up, but I think the gain in shot cycle feel will be greater the shorter the stroke, the stiffer the spring (and consequently, the lesser the preload).
     
  13. RobF

    RobF Administrator Staff Member

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    In my experience, feel gets better the longer the stroke and the weaker the spring. Short & stiff setups feel too snappy for my liking and make the pellet harder to track. We worked on an LGU recently and despite the power not changing it was far easier to follow pellets at 55yds than it was with a shorter stroke and a spring under greater stress.
     
  14. Airlexx

    Airlexx Member

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    Well Dan, if it is coincidence it’s stretching for quite a bit
     
  15. Airlexx

    Airlexx Member

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    Only down side is that i only wil benefit from it when shooting FT cuase mij rangefinding skills are dismal!
    But on paper out to 50 meters it works great
     
  16. Malcolm lockhart

    Malcolm lockhart Member

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    My two pence worth,,,, after extensive work, and still on going, on a JT lgv tune, I'm inclined to go with the barrel vibration theory.
    Dropping down to 10/10.5 with exacts, caused a jumpy, hard to shoot, hold sensitive gun.
    Increasing preload smoothed the cycle out, and made it easier to shoot. 18/35 degrees 775/755 approx, can shoot all positions with very little poi movement.
    So inclined to think a balanced movement, rather than a speed. With the accepted tolerances of cause.
     
  17. Nomads HFT

    Nomads HFT Well-Known Member

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    I recently carried out a recoil cycle velocity test with an LGV fitted with a soft spring, Rob, and all rifle movement ceased just over 100 milliseconds (ms) after pellet exit, which is ~150 ms before the pellet reaches 50 yards so, with a decent scope focussed on the target, you should see the pellet.

    LGV long scan.JPG
     
    Last edited: Jul 4, 2018
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  18. RobF

    RobF Administrator Staff Member

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    Nice. The wonder how that varies with stroke.

    One thought I have is that although the motion might be over before it hits it might be the scope isn’t looking where it was and the eye & brain too long to recover onto the spot where the hit occurs
     
  19. Cooper_dan

    Cooper_dan Well-Known Member

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    If you ever want to do that test with a TX with MK2 piston and spring let me know. Got a standard stock and a weighted stock too. I bet stock weight will show a difference
     
  20. FPoole

    FPoole Active Member

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    I don't care how smooth and calm my gun is, I don't have the eyesight to see the pellet. With scope at 32x and the sun behind me, I see the pellet diving in from above and the seemingly huge curve from a crosswind. Makes me wonder how I hit anything.
     
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