drop of bullet at 1000 yds

Discussion in 'Long Range Hunting & Shooting' started by ann brezinski, Oct 17, 2013.

  1. ann brezinski

    ann brezinski Well-Known Member

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    saw long range purist the other day.they in thier tech part said the earth in shooting to 1000 yards if you shoot to the east then shoot to the west the bullets will drop a certain way because of the earths rotation.how would you figure this in to your drop figures in shooting at game?i do not see any of the shows adreeing this in their presentations.
    gary b...
     
  2. BrowningBanger

    BrowningBanger Active Member

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    The Coriolis effect is that of the earths rotation on a target while the bullet is in flight.
    The best way to understand is to realize that the bullet leaves all contact with the earth the moment it leaves the barrel. While suspended in air, the earth is rotating underneath the bullet. When shooting west, the target (in contact with the earths surface) is rising due to the direction of the earths rotation. (Think sunrise and sunset, as the sun is essentially blocked out during sunset) Realize that this has nothing to do with the drop or path of the bullet, but rather the target moving. When shooting West, the target rises, and in order to compensate for this movement, you must Dope for a more exaggerated bullet drop. Most good ballistic programs have an additional data input regarding Coriolis effect. Long range shooting is all about understanding the different effects of atmospheric conditions, as well as how to utilize some very cool software. If shooting at ranges long enough to play with the Coriolis effect, every last thing comes into play.
     

  3. MontanaRifleman

    MontanaRifleman Well-Known Member

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    In the Northern hemisphere it also cause drift to the right which is also the same direction of spin drift in a right twist barrel.

    Here ya go...

    [ame=http://www.youtube.com/watch?v=jX7dcl_ERNs]Demonstrating how Coriolis effects bullet drop at 1000 yards - YouTube[/ame]

    [ame=http://www.youtube.com/watch?v=9P9XKbYa--g]Coriolis Effect on Long Range Rifle Shooting Ballistics - YouTube[/ame]

    [ame=http://www.youtube.com/watch?v=ouOYAlcvwOQ]Coriolis Effect in Long Range Shooting - YouTube[/ame]
     
  4. wbm

    wbm Well-Known Member

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    I wouldn't factor compass direction effect for hunting game at all. Temperature, wind and elevation will have more impact on bullet trajectory than the earths rotation.
     
  5. MontanaRifleman

    MontanaRifleman Well-Known Member

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    You need to factor in ALL the factors
     
  6. BrentM

    BrentM Well-Known Member

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    Time of Flight, TOF is the most important aspect to consider before addressing CE, in my opinion. If you have 1 second TOF it is not going to have much affect. 5 seconds, it will have more. Therefore the further you shoot the more the variables play a role in LR accuracy.
     
  7. Scrubbit

    Scrubbit Well-Known Member

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    Two components to Coriolis. Horizontal defined by latitude (dist from equator) and vertical defined by direction you are shooting. Best explanation is from Bryan Litz in Applied Ballistics. I always use horizontal component on long range shots due to my high latitude. Use vert component unless shooting North/South so effect is zero. Coriolis and spindrift are significant at extended ranges.
     
  8. BrentM

    BrentM Well-Known Member

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    Good info. I play with this in my program all the time and try to figure the affects in different situations etc. I thought the first vid was really good regarding E and W shots. What I have tried to understand is how the bullet is affected at lets say 45degrees of those, half value.
     
  9. Scrubbit

    Scrubbit Well-Known Member

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    Just for interests sake, at 1000m shooting Berger 215g hybrids out of a 300 Win Mag at 3000 fps gives a combined coriolis and spin drift of 10.6 in or .3 Mils. Definitely significant. 6.5 in is spin drift, and the remainder coriolis.
     
  10. joeycoates

    joeycoates Well-Known Member

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    I am an officer in the Field Artillery branch of the Army. If you think that the Coriolis Effect makes a difference at 1000 yards you should see what it does at 20 kilometers.... Man this takes me back to doing manual computations and the Tables, GFT's, figuring square weight. There are sooo many things that come into effect with long range shooting, it is a whole different world.
     
  11. wbm

    wbm Well-Known Member

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    We are talking about "shooting at game" here right?

    Well as long as you are going to figure out "All the factors" don't forget powder position sensitivity. That can be a real biggie too.

    Just a guess on my part but once you zero your weapon at 1000 yards, fire for effect and hit the x-ring, game animal, or enemy combatant (if you are firing a 155 for example) you probably have or wittingly or unwittingly properly applied all the factors to your weapon of choice.

    Course you could always calculate "All the factors" in the field depending on the direction you are shooting. Armed with a good compass and taking into account declination, spin drift etc. Your game animal may be in the next state by the time you shoot but what the heck at least you will have all the correct data.
     
  12. BrentM

    BrentM Well-Known Member

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    baaa haaa haa, trouble maker. I tend to load my data in the computer at first light and while in the field I double check it. Then if a firing solution is needed it is much quicker and simpler. Of course I have my chart as well, for known elevation. Correct me if I am wrong but if your properly load your data it is not that time consuming to get a good solution. For me I have data perimeters loaded in with the variables being range, slope, absolute baro, temp, wind speed, wind direction, and CE. I can load absolute first thing at the hunting site, as well as temperature. That leaves range, slope, wind, CE. I can get range and slope from the Leica with a press of 2 buttons. The rest hardest part is CE. Lat is already loaded. so I need 1 numbers, compas direction, that I would not normally input if CE was not accounted for, correct? When in the field I time myself for practicality sake. It does take a little time for sure, but I guess after all if you are shooting a 1000 yards it is about the shot and not the hunt so it better be a good one.
     
  13. MontanaRifleman

    MontanaRifleman Well-Known Member

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    So you're saying don't worry about having all the correct data because your game might be in the next state? Your not going to bother applying spin drift and coriolis that would account for 10 inches of drift @ 1000yds because you're in a hurry? That's a good way to end up with a gut shot animal or complete miss which would be no better than not shooting at all.
     
  14. wbm

    wbm Well-Known Member

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    I don't think you read with understanding to well. You sight in your rifle before you hunt. You don't sit and try to account for spin drift and which direction you are shooting before you shoot at your game....well at least I don't.

    Let me put it another way. How many times have you ever heard "Oh hell I blew the shot of a lifetime because I set my scope to shoot West and the deer was to the East. Forgot to reset my scope to account for spin drift variance. "