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Need Formula or Data for Ballistic Bore Friction

  1. Mar 25, 2007 #1
    Hello, I'm a college student in the last semester of my second year working towards my degree in Mechanical Engineering. I'm working on a project for my ODE (Math-222m) class involving the mathematical modeling of the internal ballistics of the common Spring/Air pellet rifle. I've got basically all the necessary physics formulas down for building the model (Spring Energy Equation / Ideal Gas Law / Linear Kinetic Energy / Rotational Kinetic Energy / etc.) except for one. I need a formula for the work done (obviously negative work done) by the bore friction during the pellet’s trip down the barrel. I've done a lot of searching but so far have yet to dig up any hard math or even imperial data -- All I've found so far is general references. Example, "Our pellets; due to their special . . . . coating reduce bore friction significantly and can result in some cases of a velocity increase of up to 20%" That don't help me at all I need the hard stuff, not this watered down junk. So far I’ve learned that there seems to be a direct relationship between the magnitude of the contact surface between the pellet and the barrel and the magnitude of the bore friction force opposing the pressure force induced by the compressed gas. This contact surface could be easily built into the model as a property of the individual pellets but I need a way to calculate the magnitude of the resulting friction force.

    Help !!!
  2. jcsd
  3. Mar 25, 2007 #2
    You need a ballistics handbook like Oerlikon Pocket Book or Rheinmetalls' Handbook on Weaponry.

    If you haven't got access to them, tell me and I'll send you the relevant pages. I can not attach the file here because the relevant pages are in a 10 MB Word file.
  4. Mar 25, 2007 #3
    I'll see if the college library can't get them in on the inter-library loan program. It's really annoying how the college libraries don't have squat on anything gun related, unless of course it's anti-propaganda :grumpy: :mad: . I mean -- ballistic engineering is a legitimate intellectual field as well isn't it?

    As far as getting me the files I've sent a PM to you with my two email addresses. If either of the email systems will accept them as an attached file that would be great I'm not sure what the upper limit is for file size but 10 MB might be cutting it close. Thanks !!!
  5. Mar 25, 2007 #4

    Check PM
  6. Mar 26, 2007 #5
    Thanks a million, sunday, that was exactly the information I needed. A little bit of algebra and everything was A-Okay -- just as you said it would be. :smile:
  7. Mar 27, 2007 #6
    You're welcome, but be advised I'm more of a dilettante in ballistics, i.e. I have this data in order to understand design principles of weapons, not to engineer guns by myself. As you see there is a lot of empirical know-how, and simplification involved, as engineering should be. But for the purposes of an academic exercise in diff equations is good enough.

    Also, you may want to check your solution with the examples that appear on the text. See section 4.1.3 of the Oerlikon book, for instance.
  8. Dec 10, 2007 #7
    Hi Sunday,

    I work in the Aerospace industry in armor design. I've been looking for the rheinmetal and Oerlikon handbooks off and on for years. do you know anyplace i caould contact to obtain copies of them?

    thankyou for your time.

  9. Dec 10, 2007 #8
    Check PM
  10. Mar 16, 2010 #9
    I am also in need of the same handbook, have been looking around and found this forum, has anybody still got it???? Any help or direction would be highly appreciated....
  11. Mar 16, 2010 #10
    Im actually also in the process of gathering said information, but for some reason it is really hard to come by - so if anyone could lend me a hand :)
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