GUN how long does a bullet accelerate ?

Discussion in 'On Topic' started by smell my finger, Jan 31, 2003.

  1. smell my finger

    smell my finger strive nonetheless towards beauty and truth,

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    once the charge goes off behind a bullet, how long before that bullet reaches top speed ? the length of the barrel ? 1 inch ?
     
  2. taco

    taco Guest

    the length of the barrel and maybe a fraction of an inch past the barrel. it takes pressure behind the bullet to make it go faster.

    after it leaves the barrel is has nothing to push it faster and only has wind resistance to slow it down.
     
  3. footratfunkface

    footratfunkface New Member

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    well, that and the fact that rifle loads have a lot more powder behind the round, and often have smaller weights.
     
  4. Eric1855

    Eric1855 In Hoc Signo Vinces

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    The bullet will accelerate the length of the barrel. Then after there is no back pressure it will lose velocity as well as start to fall downward as gravity affects its flight path.
     
  5. footratfunkface

    footratfunkface New Member

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    so you're saying that, no matter the muzzle velocity, the ballistic coefficient, or any other variable, all bullets will hit the ground in one second when fired from 9.8 metERs. damn australians. spell it right. m-e-t-e-r.
     
  6. taco

    taco Guest

    if I drop a parachute from 9.8 M-E-T-E-R-S will it hit the ground in a second??
     
  7. taco

    taco Guest

    9.8 meters is the rate of acceleration. with wind resistance it will not do this. it doesn't matter if the parachute opens or not.
     
  8. footratfunkface

    footratfunkface New Member

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    yeah, i'm a jackass. i forgot my physics. sorry.

    edit: but i just realized that most bullets don't follow a flat trajectory. if they did, then they'd all hit after a second. but, most rise quite a bit, then fall. i'm sure that plays with the falling time just a bit.
     
  9. KW

    KW Guest

    No bullet "rises" per se after leaving the barrel. The reason you see the +'s on ballistic charts is that the scope used to zero the weapon is mounted above the bore of the weapon. Thus in order for the gun to strike the point of aim, the scope is actually pointed downward slightly. As a result when you aim at an object at the same elevation as you, the barrel of the weapon is actually aimed up slightly ... so the weapon isn't being fired at a flat trajectory.
     
  10. footratfunkface

    footratfunkface New Member

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    no. bullets have an arched trajectory. which is why my enfield will shoot VERY high at 100 yds., and a little high at 200. but, the .303 rd. should hit pretty dead on at 300 yds. the .50 BMG is one of the flattest trajectories. and .308 is one of the most arched. for instance, i believe that the average .308 has a peak of over 2ft at its highest point above the starting elevation.
     
  11. KW

    KW Guest

    I wasn't saying bullets don't have an arched trajectory. What I am saying is that there will be no upward vertical movement beyond the angle at which it was fired. Thus is you aimed a rifle perfectly horizontally ... as in put a level on top of the barrel and made sure it was perfectly horizontal ... the bullet's path would never be above the barrel. The only force acting on the bullet in a vertical direction is gravity, pulling it downward. The only other forces acting on it are it's propellant (while it is still in the barrel) which has no vertical component in our example only horizontal, and air resistance which acts opposite to its direction of travel (and is only strong enough to make minor alterations to its path).

    Another example would be if you fired the gun at a 10 degree upward angle. If you drew an imaginary line out of the barrel at that angle, the bullet would never be above the line. Sure the bullet would be above the barrel during part of its trajectory(since the barrel was point upward after all), but it would never be above that line we drew.

    Check out this site. http://members.aye.net/~bspen/trajectories.html

    Look at the pictures he has on there. On each one he has a zeroed trajectory, and a basic trajectory. The zero trajectory shows the path of the bullet if you sighted the gun to hit the scopes aiming point at that given range. The basic trajectory shows the path of the bullet if the rifle were fired perfectly horizontally.
     
  12. footratfunkface

    footratfunkface New Member

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  13. TheProwler

    TheProwler Active Member

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    Wrong. You could have a gun 1 meter above the ground and fire it at 17,500mph and it would never stop falling (orbit, my man, orbit).
     
  14. footratfunkface

    footratfunkface New Member

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    it would, however, strike quite a few things on its way around the not-so-perfectly-flat earth. and i'm not up to date on my physics, but is the orbit velocity really that slow at such a low altitude?
     
  15. TheProwler

    TheProwler Active Member

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    The orbit velocity does change a bit, but that's close - you'd have to shoot it a bit faster for it to escape the air resistance (I was neglecting that fact).
     

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