In order to participate in the GunBroker Member forums, you must be logged in with your GunBroker.com account. Click the sign-in button at the top right of the forums page to get connected.
Options

Coriolis effect

MVPMVP Member Posts: 25,074 ✭
edited December 2015 in General Discussion
I had a long range shooter tell me about how the earth rotation affects bullet impact. Any of you long range guys notice different POI while shooting east vs west?
· Share on FacebookShare on Twitter

Comments

  • Options
    Wild TurkeyWild Turkey Member Posts: 2,427 ✭✭✭✭
    edited November -1
    Long range artillery -- like the "Paris Gun" -- has to take the earth's rotation into consideration.

    Long range tank rifles -- like the old M60A3's 105mm sabot -- had to take the spin of the projectile into consideration at about 3000m IIRC

    But at small bore rifle ranges I'd be curious as to how it's measured.
    · Share on FacebookShare on Twitter
  • Options
    nordnord Member Posts: 6,106 ✭
    edited November -1
    East west isn't the problem. North south or reverse is a potential problem as the earth revolves and moves the target away from the actual impact point.

    For our purposes with light calibers the flight time of our projectiles is minimal enough so as not to present appreciable problems. Heavier weapons are different with projectile flight times being of rather long duration.

    Throw into the mix the fact that the surface of the earth is traveling at different speeds as latitude moves from poles to the equator. Thus, at far northern or southern latitudes the earth will move very little in comparison to movement at the equator.
    · Share on FacebookShare on Twitter
  • Options
    Gregor62Gregor62 Member Posts: 3,071 ✭✭✭✭
    edited November -1
    Wouldn't POI be more affected on North vs South, since the earth rotation is West to East? Just curious.
    · Share on FacebookShare on Twitter
  • Options
    Gregor62Gregor62 Member Posts: 3,071 ✭✭✭✭
    edited November -1
    quote:Originally posted by dennisnielsen
    quote:Originally posted by stubnoid
    Wouldn't POI be more affected on North vs South, since the earth rotation is West to East? Just curious.


    I have always wanted to ask that question


    Well Nord answered it 3 100ths of a second before my post. I guess the Coriolis effect works on the net too.[:)]
    · Share on FacebookShare on Twitter
  • Options
    MVPMVP Member Posts: 25,074 ✭
    edited November -1
    I will admit I laughed when he was telling me that the earth rotation had an affect on bullet drop and drift depending on east,west,north and south.
    According to his tests at 1000 yards, the bullet POI can change more than a few inches up and down when shooting east vs west. and right to left when shooting north vs south.
    When I realized he wasn't joking, it sparked an interest to know more.
    · Share on FacebookShare on Twitter
  • Options
    mogley98mogley98 Member Posts: 18,297 ✭✭✭✭
    edited November -1
    According to this data east and west are effected up and down and north south left to right for different reasons.

    http://thearmsguide.com/5329/external-ballistics-the-coriolis-effect-6-theory-section/
    Why don't we go to school and work on the weekends and take the week off!
    · Share on FacebookShare on Twitter
  • Options
    MVPMVP Member Posts: 25,074 ✭
    edited November -1
    quote:Originally posted by stubnoid
    Wouldn't POI be more affected on North vs South, since the earth rotation is West to East? Just curious.
    He explained to me that the target will rise if you are shooting east and drop are shooting west. I don't know?
    · Share on FacebookShare on Twitter
  • Options
    CubsloverCubslover Member Posts: 18,601 ✭✭
    edited November -1
    Fun fact:

    We use this principle to measure the mass flow of a liquid through a pipe. A tube vibrates with liquid in it while sensors pick up the vibration and frequency from each end. When flow starts, each end vibrates the the same frequency, but off a number of degrees. When the liquid thickens, the deflection and frequency changes.

    Measuring this and using calibration data, we can determine the flow rate both volumetrically and by mass.


    Nerd read over. Sorry, it's kinda in my field.
    Half of the lives they tell about me aren't true.
    · Share on FacebookShare on Twitter
  • Options
    guntech59guntech59 Member Posts: 23,187 ✭✭✭
    edited November -1
    Basically the target moves in relation to the line of flight. The greater the distance, the greater the change in POI.

    Artillery FDC computers and Naval guns have this accounted for in their solutions.
    · Share on FacebookShare on Twitter
  • Options
    Smitty500magSmitty500mag Member Posts: 13,603 ✭✭✭✭
    edited November -1
    Bridge designers that are designing long bridges have to figure in the earth's curvature. I would suppose anything long range would be effected somewhat.
    · Share on FacebookShare on Twitter
  • Options
    Wild TurkeyWild Turkey Member Posts: 2,427 ✭✭✭✭
    edited November -1
    Demonstrating how Coriolis effects bullet drop at 1000 yards

    https://youtu.be/jX7dcl_ERNs
    · Share on FacebookShare on Twitter
  • Options
    bpostbpost Member Posts: 32,664 ✭✭✭✭
    edited November -1
    The Coriolis effect explains my misses of the 10 ring for the past 50 years of shooting.
    · Share on FacebookShare on Twitter
  • Options
    nordnord Member Posts: 6,106 ✭
    edited November -1
    East/west will be affected as the earth rotates west to east. As with north/south the degree will be affected by latitude. My late father was a forward observer in a heavy artillery unit during WW2. East/west was compensated (105 & 155's) by ranging the guns before they went into the field. He shared that of six guns one could pretty much assume two would be short, two on, and two over.

    Only on the really heavy stuff would there be any appreciable Coriolis problem as the slightly differing guns would take care of the earth's movement. That and a spotter to correct firing info.

    Flight time is the key. The longer the flight time the more movement underneath the projectile. My understanding is that north/south is more of an issue as range can be spot on yet the target will have moved considerably.
    · Share on FacebookShare on Twitter
  • Options
    Gregor62Gregor62 Member Posts: 3,071 ✭✭✭✭
    edited November -1
    quote:Originally posted by dennisnielsen
    quote:Originally posted by stubnoid
    quote:Originally posted by dennisnielsen
    quote:Originally posted by stubnoid
    Wouldn't POI be more affected on North vs South, since the earth rotation is West to East? Just curious.


    I have always wanted to ask that question


    Well Nord answered it 3 100ths of a second before my post. I guess the Coriolis effect works on the net too.[:)]


    I am way slower than you [;)]



    Old happens![:D]
    · Share on FacebookShare on Twitter
  • Options
    chiefrchiefr Member Posts: 13,801 ✭✭✭✭
    edited November -1
    The coriolis effect It is so minimal for small arms, it has not effect at all. If you know the time of flight and distance, you can trig it out.
    It does matter with artillery that fires great distances.
    · Share on FacebookShare on Twitter
  • Options
    TempestTempest Member Posts: 1,273 ✭✭✭✭✭
    edited November -1
    I shoot to 1250 yards often and don't account for it. Wind and spin drift have more affect. I'm sure at some point (mile or more) you might have to correct for it before you take a shot.
    · Share on FacebookShare on Twitter
  • Options
    TheBrassManTheBrassMan Member Posts: 3,808 ✭✭✭
    edited November -1
    I prefer this effect on shooting[:p]

    https://www.youtube.com/watch?v=uLJjY44X_0M
    · Share on FacebookShare on Twitter
  • Options
    11b6r11b6r Member Posts: 16,588 ✭✭✭
    edited November -1
    Spin drift will have a much greater effect than the Earth's rotation, unless you are firing REALLY long range.

    It was built into the firing tables for the 4.2 mortars (being a rifled mortar) They could reach 5,600 meters. The artillery had a more pronounced effect, since the 175s could reach as far as 32,800 meters.
    · Share on FacebookShare on Twitter
  • Options
    yoshmysteryoshmyster Member Posts: 21,116 ✭✭✭✭
    edited November -1
    Got to get your inner Muslim on and face Mecca.
    · Share on FacebookShare on Twitter
  • Options
    fugawefugawe Member Posts: 1,540 ✭✭✭
    edited November -1
    Basing everything on being at the equator, where you are moving at approximately 1000mph in rotational speed, I always figured a west-east shot would hit higher at long distance than an east-west shot due to 2000mph difference in velocity. The effect here being the higher centripetal force shooting west-east.
    · Share on FacebookShare on Twitter
  • Options
    mogley98mogley98 Member Posts: 18,297 ✭✭✭✭
    edited November -1
    For those who claim no effect at 1000 yards that makes no sense based on this data from the link I provided,


    "a .308 175gr bullet, with a muzzle velocity of 2700fps, from a latitude of 45?. The drop at 1000yds will be 392 inches, North or south.
    Shooting eastward, the drop will be 388in.
    Shooting westward, the drop will be 396in. In either case, there is a total change in drop of 4in."

    Seems to me not accounting for 4 inches equals a miss.

    Also North to South

    "firing the same .308 175gr bullet at 2700fps muzzle velocity, from a latitude of 45? in the Northern Hemisphere, the deflection at 1000yds will be of 3in to right. At the North Pole, where the effect is maximum, the deflection will be a little more than four inches. The deflection will be the same in the Southern Hemisphere, but it will be to the left, instead.

    So 4 inches left or right and 4 inches up or down unaccounted for is a huge miss IMHO.
    Why don't we go to school and work on the weekends and take the week off!
    · Share on FacebookShare on Twitter
Sign In or Register to comment.