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Thread: Bullet acceleration/deceleration?

  1. #1

    Bullet acceleration/deceleration?

    I just had an interesting debate with a group of engineers as to when a bullet begins to decelerate!
    Let's just say that 'opinions were varied'!
    So is it:
    1. Whilst still in the barrel?
    2. Exactly as it leaves the barrel?
    3. A short time after it leaves the barrel?
    4. A good while after it leaves the barrel?
    5. When it hits the target?
    6. Depends whether you fire up or downhill?
    7. Depends upon the length of the barrel?
    8. Depends upon how fast your powder burns?
    8. Depends whether you have a moderator fitted?
    9. I don't really care, my brain hurts!
    MS

  2. #2
    9 lol

    It would probably take in a few aspects mentioned in the list above but havent got a clue what ones. I'm guessing barrel length and powder burning speed would come into it? It would be interesting to know right enough.

  3. #3
    I would think that it either starts to decelerate either in the barrel or on leaving the barrel depending on barrel length and burn rate. It cannot maintain muzzle velocity after leaving the barrel as the forces acting on it are gravity wind and drag.

  4. #4
    Quote Originally Posted by pete evans View Post
    It cannot maintain muzzle velocity after leaving the barrel as the forces acting on it are gravity wind and drag.
    What about the gasses which leave the muzzle behind the bullet which are still expanding rapidly?

  5. #5
    Quote Originally Posted by Monkey Spanker View Post
    I just had an interesting debate with a group of engineers as to when a bullet begins to decelerate!
    Let's just say that 'opinions were varied'!
    So is it:
    1. Whilst still in the barrel?
    2. Exactly as it leaves the barrel?
    3. A short time after it leaves the barrel?
    4. A good while after it leaves the barrel?
    5. When it hits the target?
    6. Depends whether you fire up or downhill?
    7. Depends upon the length of the barrel?
    8. Depends upon how fast your powder burns?
    8. Depends whether you have a moderator fitted?
    9. I don't really care, my brain hurts!
    MS

    it definitely depends on whether you count the number 8 twice in the calculations.....

    bullet may actually still increase in V as it leaves a high friction environment into a low friction one until the effect of the air resistance becomes greater than the acceleration as it leaves the muzzle

  6. #6
    It stops accelerating when the expanding gases from the burning powder stop exerting a force high enough to counteract barrel/air friction and gravity on it. After that, it's in freefall.

  7. #7
    Quote Originally Posted by Monkey Spanker View Post
    What about the gasses which leave the muzzle behind the bullet which are still expanding rapidly?
    with no barrel bullet seal to create pressure i doubt it would have any measurable effect.

  8. #8
    Option 3
    (The Unspeakable In Pursuit Of The Uneatable.) " If I can help, I will help!." Former S.A.C.S. member!

  9. #9
    When it loses the propellant force necessary to overcome forces of environmental drag, whether that be barrel, air pressure or any media the bullet might be passing through.~Muir

  10. #10
    Quote Originally Posted by finnbear270 View Post
    Option 3
    I'm with Finnbear on this one, having exhausted its propulsion and having hit the resistant of the air I would think choice three.

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