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Discussion in 'Long Range Hunting & Shooting' started by Straight Shooter, Sep 21, 2019.
If you are shooting north and south at 1000 yards , how do you figure this in?
I don’t. Not at the latitude I’m at for that range. It is small enough to the right that none of my scopes can adjust for it (1/4 moa or 1/10 mil) when shooting N to S or vise versa (other azimuth can effect elevation adjustment). It will always be to the right here in the northern hemisphere. At that range I will account for some spin drift (also to the right with my right twist barrel). An example with one of my rifles; it has not quite 1/2 moa right drift at that range, I will put on .5 L to cancel out both. This will put me very close to theoretical center and I can put the focus on my wind call. If I were to move to the North Pole I may add 1/4 moa or 1/3 mil.
When the ranges get much further I will account for it, but rely on my good ole ballistics app for that.
At 1000 yards the difference is enough to ignore. There are 2 components, vertical and horizontal. When shooting north south there is no vertical component anyway. When shooting anything that'll reach 1000yrds while still supersonic there's no horizontal component that you could reasonably correct for until you start getting into artic/arctic latitudes.
If you want to simply find out what the error contribution of Coriolis is separate from all other factors then you can download my free spreadsheet from https://ballisticxlr.com/ballisticxlr-support/ and you'll find it on the Table 100 Full Sheet and the Table 10 Half-Sheet tabs.
BallisticsGuy, from my teachings coriolis is the L/R displacement and eotvos is the elevation aspect. Is that what you (or maybe others on here may chime in) have heard it referred to?
Yes. Calling it vertical coriolis isn't probably the best term to use but because the effects are related to the movement of a projectile in free flight over a revolving earth it's convenient and not too far from absolutely correct. That and nobody knows how to pronounce Eotvos or how to make the o's come out with umlauts.
Do you have an app like Applied ballistics or the sort? I myself do not enable Coriolis in mine. I also use a Kestrel 5700 with AB, I just went through it, I'm not 100% that it figures it in the calc.
If you do have an app, enable it, then change your azimuth and see what it does to your dope. It does not change much for me to 1000 yards, I can expand the number, but to me, the farther one goes out, the more in question your load becomes as to how well it holds vertical. Then throw in environmental conditions which skew things way more.
Just say you shoot at 1600 yards. And your 3 shot group size is 12", the bulk of that will be vertical dispersion unless you are shooting a cheytac sizes case, There are days, same rifle, same load that may disappear, but there is so much going on when the bullet is in flight that Coriolis is something I will never concern myself with. I suppose if I entered the 2 mile game, my mind may change.
In the northern hemisphere, northerly moving air is deflected to the east, and southerly moving air is deflected to the west. Because cyclones have a low pressure zone in their center, moving air (that would otherwise equalize that pressure) is at once deflected away from the center by the Coriolis force (keeping the low pressure zone low), and pulled toward it due to the fact that it is a low pressure zone. The Coriolis force also drives circular airflow around high pressure zones too (these are called anticyclones), but these weather systems are not as dramatic because the Coriolis force and the pressure gradient force don't oppose one another; they both work to dissipate the anticyclone. (you will want to check this out for yourself as I am not an expert in atmospheric physics) A Foucault pendulum is actually subject to the centrifugal force in addition to the Coriolis force, though the centrifugal force due to the spinning earth is rather small, and is easily accounted for by slightly adjusting the "constant" value of the acceleration due to gravity. The Coriolis force is exclusively responsible for changing the direction a Foucault pendulum swings in over time.
Ask a simple question, get an over intellectualized answer.
Just kidding man.
I really don’t even know why I’m reading this other than to learn new info.
Even after googling, I still don’t have a good understanding of what this is.
Can one of you give a short, basic definition/description for those of us who are confused?
Simple version, the earth rotates west to east. In essence, your target is always moving, so bullet flight time dictates just how much it moves. Don't get too worried, if shooting due north or south, it is an inch and half at 1000 yards. Even at 2500 yards, it is under 5". That is why it doesn't come up much.
Some claim vertical discrepancies when shooting in certain directions, but once you start shooting so far, over 1K, way more things to concern yourself with. If you shoot off a phone app, most likely you can enable the feature, if you do, just play with it, shooting in all directions. Disable spin drift and make sure no wind is entered too.
Google, then download Hornady 4 DOF. You will get a mathematical answer. If you want to truly understand, it will take a little effort.
Well Think of it this way, you and your target are stationary objects on a spinning ball. Both are constant and not moving. Now when you shoot, the bullet is "in flight" AS the ball keeps spinning. On VERY long shots as you can imagine that fraction of a second in "flight time" is enough to measure the distance the ball rotated "underneath" the flying bullet... Make a little sense?
VERY simple ( REVIC SCOPE )
Best Q & A in a long time. Thank you.