How long does a rifle bullet take to travel a mile?

Discussion in 'General Gun Discussions' started by Flechette, Jan 14, 2017.

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  1. strambo

    strambo Member

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    No real affect on "lethality" but a big affect on the terminal ballistics. A bullet which will fragment and cause a huge temporary cavity above 2000+fps, at 1300 or less will only punch a hole right through them. But, they are still getting a 175g (or whatever weight) .30 cal hole punched through them, perhaps a tumble or 2 on the way through as well.
     
  2. Chemistry Guy

    Chemistry Guy Member

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    The calculus is not all that difficult for this problem, but there are a lot of assumptions that need to be clarified. Are you interested in the total distance the bullet travels, or in the arc connecting two points a mile away from each other? If you want to do a very simple approximation and you know the muzzle velocity as well as the velocity at the target, you can use algebra rather than calculus to solve for the time of flight by assuming constant deceleration.

    If you really need the number for something and the estimation from ballistics calculators is not good enough, it is not that hard to measure the value experimentally using high speed video capture and some LED sensors, or even just the sensors if you can do a bit of programming to calibrate the system. An even easier solution is to take audio of yourself shooting a gong, and then subtract the easily calculated time that it takes the sound to get back to your microphone.
     
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  3. coloradokevin

    coloradokevin Member

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    Some people are really overthinking this one, while others are looking at it too simplistically. You can't just calculate based off of muzzle velocity, because a bullet is slowing constantly after leaving the rifle. But, you can still use a ballistic calculator for the load you are talking about, and you'll have the answer instantaneously. For example, a 140 grain Berger Hybrid Match bullet from my .260 Remington will reach 1 mile in 3.05 seconds. That number is also controlled by the atmospherics at play at the time that the shot was taken. My numbers are based on a density altitude of 7,000 feet, since I live well above sea level.
     
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  4. 1stmarine

    1stmarine Member

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    I agree, of course people are over thinking this one.

    We have to assume anyone interested in finding out the answer will have to know something and/or have the means to take some measurements.

    So lets assume we do not have a Doppler radar that is the best way to measure the trajectory and time of any shots with their differences.

    Lets say you know the load starting speed, bullets, atmospherics and the distance that is one mile that is 1760 yards.
    Since you know the distance and the bullet you can get a ballistic table for that shot like others suggested..
    Any decent ballistic calculator will tell you the time.

    If your ballistics software does not have time and don't care to use another one or you
    are bored and need something fun to do, you could also do some simple algebra to calculate the time based
    on the deceleration.

    A = acceleration
    V = Final speed
    U = Starting speed
    S = Distance
    T = Time

    A = ( V - U ) / S ... this will result in a negative numbers and don't forget to convert yards to feet so
    then you can divide from your foot per second difference.

    By the same token deceleration can be calculated from two speeds at a known distance.
    A = ( V² - U² ) / T
    So
    T = ( V² - U² ) / A
    but this time will not be precise because pretty much depends on trajectories and deceleration from
    a flat line (like a car stopping) that is not what we are doing. Yes there is a 1760 straight line but the parabolic trajectory is a longer
    distance so the deceleration must be corrected with a factor that is a function or retardation coefficient for that distance.

    For example for a 50 BMG with a match bullet at lets say 2800fps you will have a very flat trajectory with
    a G1 coefficient of 1.050 like the hornday. In this case the time estimated from the deceleration will only need a
    2% factor deviation from linear deceleration. But if you go to a 150gr 308 that factor might be as high as 44%
    that is proportional to the extra distance imposed by a very pronounced parabola to get to that mile with
    such bullet and with considerable angle. This si why linear deceleration cannot be easily applied but
    you can get close with proper adjustments.

    There is also the issue about the shooting angle. Virtually any target can be hit with
    the same bullet, firearm and distance at two completely different times with radically different angles.
    Nobody is going to do that unless there is a scientific reason or we were in the navy talking about TAT tactics.

    Another thing you can try is sound. Given you can capture the flash and bullet report at a known distance
    you can back track and calculate this way. Same thing from a shooting position if you can hear the report
    from a target. A camera or recorded could be edited and then taking the atmospheric data and wind
    into account these sounds in a sound file could provide the reference points to do the calculation
    with sound. Same concept when we count seconds to calculate the distance of a storm. One would
    actually use sound to calculate time but wiht some devices in order to be accurate to 1/10-1/30 of a second
    or so I would say depending on what you use to record it. sound and video files seem they could be detailed enough.

    Manual stop watch will put too much human error but better than nothing I guess.

    While unnecessary these could be fun exercises for kids to practice algebra or anyone interested in
    going bare-bones yukon style.

    ...just my 2 cents..
     
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  5. jerkface11

    jerkface11 Member

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    I've yet to see a ballistic calculator that doesn't give you time of flight.
     
  6. 1stmarine

    1stmarine Member

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    some of the free ones and online ones like hornday.
     
  7. jim in Anchorage

    jim in Anchorage Member

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    Well you saw want happened when I asked what a MOA is. In no time I was a expert on long range naval bombardment.
     
  8. Pete D.

    Pete D. Member

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    Interesting. My ballistics program gave a much different time of flight. 3.68 seconds for one mile for the Barnes 647 grain TSX at 2700 fps MV.(BC .563)
    For the Hornady 750 grain A-Max (BC 1.050) the TOF was 2.72 secs
    Using a BoreTech 792 Match (BC 1.124) gave a result of 2.65 secs....at 2600 fps the TOF was/is 2.77 secs.
     
    Last edited: Jan 20, 2017
  9. BigBore44

    BigBore44 Member

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    Yep. I'm not even out of bed yet and this thread makes me want to drink. (Not coffee). But the knowledgeable people on this forum, never ceases to amaze me.
     
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