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I want to know about what happened when gun fired in details, please help

  1. Dec 9, 2007 #1
    Hi all,

    I want to know in detail about gun, especially the properties of gas with hight pressure like in gun's barrel. Could you give me some free useful things?

    Or just answer me some question:
    1 When firing, from the begining of the explosion until the bullet leaves the barrel, how pressure of gas is changing?
    2 How gas does when meet another low pressure way, like a tube leading the gas back in automatic assault rilfe? Is the pressure contact the bullet still the same as in case there isnt any tube leading gas back? And how is pressure in that tube, equal the barrel or not? I think when meets low pressure way like this, at first, gas will transmit almost all it's pressure to that way untill two ways have the same pressure, right?
    3 And how fast does gas changing it direction when meet another way? I remember that gas's pressure transmit in all direction, so when meet another ways, it immediately change direction with full pressure, correctly? And when in hight pressure and very fast process like this, is it still considered immediately, in comparison with the movement of the bullet?
  2. jcsd
  3. Dec 10, 2007 #2


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    Science Advisor

    1) Wjen the gunpowder ignites, the bullet is sitting still. As more and more powder burns, the gasses released attempt to expand, but the itnertia of the bullet means that it cannot start moving immediately, nor get to its top speed as soon as it starts moving. So, as the volume of gass continues to increase at a rate greater than the rate at which new space is provided by the bullet's motion, pressure continually increases. But the bullet does get moving in a pretty big hurry, and the burn of the powder is fairly quick. So, probably by the time the bullet is 1/4 of the way down the barrel (not sure how far), pressure is decreasing. However, pressure is still greater than atmospheric, so the bullet is still accelerating even though pressure is decreasing.
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