Parallax of a bullet

Discussion in 'Ruger Center Fire Pistols' started by Tommycourt, Nov 2, 2016.

  1. Tommycourt

    Tommycourt Tommycourt

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    This may be a silly question but I have to ask it. I am shooting .45ACP rounds, plated Berry, 230 grn. RN out of a 4 1/2" barrel. I understand that the bullet leaves the barrel and will rise in it's trajectory at one point and then level off again at another point. If I am shooting @30 feet at what point does my bullet start to rise and then what point does the bullet flatten out on it's trajectory again. I have heard different theories, however have never really gotten a good answer nor one that gives me the formula for figgering it out. I don't have the privilege of shooting on an outdoor range where you can go out with different spaced targets to find out for sure. And one more question, how high does the bullet rise from it's original starting point after leaving the muzzle. I realize different guns shoot differently and caliber, bullet weight, powder charge, type of powder all play into this. I just want a general idea of how to figure it out. Any answers will be greatly appreciated. And please keep them somewhat brief so my decrepit brain can absorb the info. Thanks

    Tommy
     
  2. VThillman

    VThillman Active Member

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    Tommy, have you been smoking giggle-weed again? The bullet doesn't rise after it leaves the barrel unless the barrel is pointing up. Doesn't flatten out, either. The real deal is explained in exterior ballistics. If you Google on that, the story will be told.

    Hmm... you shifty son-of-a-gun, is this part of your plan to win the decrepitude contest?

    Jim, have I lost the game already?

    [Tommy, here's a hit I got when I googled the subject. A regular guy like you and me (only clearly smarter than I), who speaks plain American - and must be tough, being a gunner who lives in MA.
    http://www.firearmsadvantage.com/about_me.html]
     
    Last edited: Nov 2, 2016

  3. Tommycourt

    Tommycourt Tommycourt

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    April 23, 2011, 09:43 PM
    Picture the bullet's path as a parabola or arc, that will cross your line of sight going up from below, then down from above. Picture, too, that the bullet's forward velocity is being constantly slowed by the drag of the air.

    Your near zero will be hit when the bullet rises to meet the line of sight. (With an AR of M16 barrel length, that's normally set at 25m.) Your far zero will be when the bullet has dropped back down to line of sight. (With an AR of M16 barrel length, with initial zero at 25m, that's normally at 300m.) Between those distances, the bullet is flying an arc, climbing above the line of sight, then dropping back to it. Past the far zero, the bullet starts dropping more rapidly, as it accelerates downward with gravity, and as its forward velocity is slowed by aerodynamic drag.

    The faster the bullet, the flatter the arc. The slower the bullet, the more a "garden hose" type trajectory is required at distance.

    Tommy
     
  4. DrDenby

    DrDenby New Member

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    Obviously you are both right.

    Obviously if your gun barrel is level the bullet will not rise.

    BUT, unless you are 10 feet away (just using as an example, obviously it can be further), you are never going to be shooting flat.

    When you sight in your gun for elevation, you are adjusting it to the right parabolic arc that will get your bullet to drop into your intended target for your target distance.

    What that arc degree is is a trigonometric calculation out of my knowledge scope (scope.. get it :duck:) though.

    Doc
     
  5. phideaux

    phideaux Well-Known Member Lifetime Supporter

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    That^^^ would have been my simplest explanation to Tommy and Bob.

    Many , many variables to consider also.

    Jim
     
  6. VThillman

    VThillman Active Member

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    I'm pretty sure now that Tommy started this as a feint in our decrepitude contest. Won points then gave them back. It ain't going to be easy, but I'm going to win this.
     
  7. phideaux

    phideaux Well-Known Member Lifetime Supporter

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    Watch out for a darkhorse in the race...;):D





    or darkdog...




    (mangled,messed up )
    Jim
     
  8. MagBlackhawk

    MagBlackhawk Patriot

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    Hey VT, You know what they say...

    If you can't run with the Big Dogs, you better stay on the porch! ;)




    :GadsdenFlag:
     
  9. VThillman

    VThillman Active Member

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    It's a conundrum. The most decrepit can't win the contest - being too decrepit to compete. I am doomed to fail.
     
  10. spikedriver

    spikedriver Active Member

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    Hang on, I'm confused...

    Maybe I have my terminology mixed up, but I thought parallax was a deviation in point of aim, caused by the shooter's eye being misaligned with the center of the aiming device?

    Maybe I just made an unintentional entry into the decrepitude contest...
     
  11. buildit

    buildit Goofy Owner

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    Had to read this exchange to make sure someone wasn't trying to conduct astronomy with a gun. :rolleyes: Parallax is a method used to calculate distances of things like other stars based upon the arc seconds it has from known distance in the earths orbit giving you two angles and one side of a triangle allowing the other legs to be calculated giving the distance to the object in space.
     
  12. DrDenby

    DrDenby New Member

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    Best layman's terms explanation I have come across.. at least in about 9 months or so ago. There might be better now.

    [ame]https://www.youtube.com/watch?v=1VPGcq9IVxc[/ame]

    Doc