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Question One for the clever people

Discussion in 'Anything Airgun Related' started by tomsteebs, Jan 19, 2014.

  1. tomsteebs

    tomsteebs Donator

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    Would it be possible (Not logical or Cost effective) to make pellets out of of light weight but strong metal/alloy which could stand up to sound breaking speeds? At relatively lower ftlb....
     
  2. Clubshot

    Clubshot Clubshot

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    Already Done by Pax -

    Dynamic Range Made out of worked Zinc - Soft but longer than Lead - as Lighter

    Also the Pax Bullet Shape can take All known Power - without damaging the pellet in flight - even in Lead

    BOB/R
     
  3. tomsteebs

    tomsteebs Donator

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    Can you manufacture or could it be possible to manufacture a pellet to go the speed of sound but be sub 12ft lb, so super light .177?
     
  4. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    It's entirely possible, however you'll end up with a projectile that's inferior to traditional lead pellets; for a number of reasons:

    1. For subsonic examples, drag increases with the square of the velocity increase - so driving stuff faster means it loses energy a lot quicker - making it more susceptable to accuracy loss and the effects of wind.

    2. When you break the sound barrier, drag increases significantly more than would be expected from a subsonic model alone.

    3. In the transonic region projectiles tend to become very unstable; with an airgun pellet (especially one that's very light and doing sub-12ftlb) you might get away with few ill effects when accelerating it through the sound barrier, however it will quickly decelerate back to subsonic velocities; which I imagine would kill accuracy.

    Basically, unless you're some uneducated yank being sucked in by all their manufacturer's BS velocity claims, you never, ever want to go past about 950ft/s with an air rifle ;)
     
    Last edited: Jan 19, 2014
  5. bobbie1

    bobbie1 Busy Member

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    Last edited: Jan 19, 2014
  6. dave goodall

    dave goodall Donator

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    u wont damage the pellet as your very unlikely to hit the target all the pax pellets are inferior to the likes of air arms jsb in reality there one the worse pellets out there H&n did a green zinc too and they were just as crap !
     
  7. dave goodall

    dave goodall Donator

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    Again as cloverleaf has said any thing over 950-976 is going to suffer accuracy in fac or sub 12 unless your american and just power mad with no thought of your quarry
     
  8. bobbie1

    bobbie1 Busy Member

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    I didn't say they were accurate , I wouldn't use them ,
    I don't shoot animals period ,
     
  9. Ballisticboy

    Ballisticboy Busy Member

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    Projectiles do not become very unstable at transonic speeds. There are thousands of projectiles all over the world of all shapes and sizes which fly perfectly happily at transonic speeds every day. Current pellet designs are unsuitable for transonic speeds because of their shape not the material they are made of. There appears to be a dynamic instability problem with the conventional pellet shape at high speeds (as opposed to gyroscopic or aerodynamic stability) but the gyroscopic stability actually increases. A lightweight pellet could be made which will work at transonic speeds but it would not look anything like a pellet.
     
  10. tomsteebs

    tomsteebs Donator

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    Oooh, that's gotta hurt clubshot, doesn't he work for umerex or something?

    And thanks for details Bob :Up:
     
  11. 177

    177 Donator

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    From memory, twice the velocity slows down 8 times faster.

    That's not taking additional sound barrier related factors into account either...
     
  12. tomsteebs

    tomsteebs Donator

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    Yep, learnt that on Guy Martin's programme the other day lol
     
  13. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    I see I've (yet again) fallen into the internet trap of posting an unsubstantiated claim :p

    While happy to bow to your superior knowledge and experience on such matters, I'd certainly say that anecdotally manufacturers seem to try and avoid transonic velocities - .22LRs will exceed the sound barrier but most manufacturers either try and keep velocities below or significantly above the speed of sound. In addition the high velocity ammuntition rarely proves to be among the more accurate flavours.

    Also conventional wisdom appears to place great emphasis on the distance at which a centrefire rifle bullet will drop below the sound barrier; with the inferred belief being that accuracy will suffer as a result.

    Finally, from various tests on American forums it appears that airguns tend to lose accuracy once pushed past the sound barrier (although as you say traditional airgun pellets are designed to operate at subsonic velocities).
     
  14. tomsteebs

    tomsteebs Donator

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    Maybe h&n rabbit magnums would work well at very high speed?
     
  15. 177

    177 Donator

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    Don't know who he is...

    I read it in one of my old rifle books years ago.

    Surprising what comes to you that you hadn't realised had lodged in what passes from my brain ;)
     
  16. Ballisticboy

    Ballisticboy Busy Member

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    Drag is a function of velocity squared so for the same Cd the drag is 4 times higher at twice the speed. Cd will not normally remain constant so the exact amount the drag increases will depend on how the Cd changes which will in turn depend on how fast you are going to start with. The drag on a tank long rod penetrator at hypersonic speeds for instance remains roughly constant as the speed drops because the Cd increases at lower velocities. There is no hard and fast rule.
     

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