Long Range shots - elevation right on always to the right

WildRose

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I meant correct yourself again.

Of course we can have a discussion and disagree without calling one another derogatory names. I have, and I can. Can you? We can have a difference of opinion. We can have different preferences. We can have different likes and dislikes. We can have different goals. Different standards. Different cares and different concerns. As you've demonstrated, we can call each other names. We can cuss until the air turns blue.

Now, when the subject matter is proven scientific and factual correctness, the options are much more restrictive. We can be correct or incorrect, right or wrong, informed or uninformed, proclaim truth or spread false information. Proven facts, science, and exterior ballistics simply are what they are. They remain consistently the same yesterday, today, tomorrow. In spite of that, we still all have the God given right to accept - or reject, at least in this country.

I haven't expressed a position that your opinion is wrong. And I haven't called you any derogatory names. If I haven't expressed myself clearly, let me do so now. I have stated, and I maintain, that much of the Coriolis Drift related information you're presenting as factual in the attempt to troubleshoot and explain the causes of rightward drifting bullets is, emphatically incorrect. And you cant change incorrect information to correct information with your changing opinion(s). The incorrect information has to be changed, in order to correct it.
Then let's correct your information.

Your computations make a lot of assumptions vs what information we have been given to work with.

They are only correct if we assume the shots are fired perpendicular to the rotation of the earth.

That is why I asked him to get us a compass reading on the direction he's shooting so we have more information to work with.
 

phorwath

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Then let's correct your information.

Your computations make a lot of assumptions vs what information we have been given to work with.

They are only correct if we assume the shots are fired perpendicular to the rotation of the earth.

That is why I asked him to get us a compass reading on the direction he's shooting so we have more information to work with.

Correct what information? Again, you'll have to further explain yourself. I provided all of the impacting assumptions that were used as input data in order to calculate the magnitude of horizontal Coriolis Drift at both 1000 yards and at 1 mile. My computations are correct for the input parameters I identified and used. If those assumptions don't match the specific conditions of the original poster, are you trying to say my information is incorrect? Here's the information I posted in Post #20:

Coriolis Drift: Input Parameters
Location = 45 Degrees North Latitude
Direction of Fire = Due East or Due West (90 or 270 Degree Azimuth)

Coriolis Drift at 1000 yds = 2.5 inches rightward drift


The Latitude location I provided and used was 45 Degrees North Latitude. The Direction of Fire was I provided and used was Due East or Due West, parallel to the rotation of the earth's rotation. And the Coriolis drift at 1000 yds is correctly calculated as 2.5 inches of rightward drift.

You've stated your understanding and position that Coriolis Drift only causes horizontal bullet drift when the direction of fire is true North (Azimuth of 0 degrees) or true South (Azimuth of 180 degrees), perpendicular to the earth's direction and path of rotation. Your understanding, and resultant position, is mistaken. Which is why you end up with incorrect conclusions, and make incorrect statements.

Coriolis caused horizontal drift is present regardless of the direction of fire, and the magnitude of the drift is determined by the location (Latitude) of the shooter on the earth's surface. The magnitude of horizontal Coriolis drift is greatest at the north and south poles, and diminishes to basically zero at the equator. I chose to use a location half the distance between the north pole and the equator, which is representative of much of the contiguous 48 States.

The compass direction isn't a factor. The information the OP would need to provide is his Latitude location. How many degrees North or South Latitude. And the Latitude is only necessary for the calculation of Coriolis drift. The calculation for the much greater source of drift, Spin Drift, isn't dependent on either Latitude or the direction of fire.

The OP is seeking an explanation, a cause, a source - for approximately 1 MOA rightward drift out to 1000 yds. What I have explained, calculated, and demonstrated, is that Spin Drift is responsible for 0.635 MOA of rightward drift, and that Coriolis Drift could very easily be responsible for an additional 0.240 MOA of rightward drift. That's a combined rightward drift totaling 0.875 MOA. My question is: Do we really need to be looking for any additional sources or causes of rightward drift? I can't spell it out any clearer. Spin Drift + Coriolis Drift = 0.875 MOA rightward drift at 1000 yds.

Do others still feel compelled to identify the source of the remaining 0.125 MOA of rightward drift based on the limited information we've been provided with thus far? It's a free country and a relatively open Forum. I'm the last person that wants to stand in the way of the exploration and pursuit of all additional potential causes that could produce the remaining 0.125 MOA of rightward drift. Let the fun continue... I'll get popcorn for the kettle... I'm game... :)
 
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Jim5351

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I would agree with the with the explanation of why the POI would be 10” to the right at 1000 yds. due to spin and coriolis drift if POI was dead on at 100 yds. However, NVHUNTER1 states that POI is 3/4” left at 100 yds. (8-24 post) and 4” rt. at 400 yds. with dead on at 200 in his opening post. NVHUNTER1 states 4”at 400yds. , 6” at 600 yds. 8” at 800 yds. a consistent 1” per 100 yds. from 400-800 yds. it would appear that at 10” at 1000yds could be attributed to drift. Those numbers represent about 1 MOA of right drift and appear to be consistent from 400-800 yds. What happened from 200-400 yds? 4” drift in 200 yds. NVHUNTER1 also states he is 3/4” left at 100 yds. which is about 3/4 MOA. It seems to me that would pretty much compensate for most of the drift, if drift was the cause of his problems. I would still check to be sure that the scope is in perfect alignment with the bore. I am sure you are dealing with more than drift.
 

fatrack

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Hey Phorwath,

I'm thinking about the Coriolis effect-

In regard to a shot along a North or South trajectory, my gut tells me the target would "move away" from the aim point faster than an East-West shot. I would even be inclined to think a East-West shot (small arms) should have negligable effect because the target is moving almost directly towards or away from the origin of fire.

Can you post a Coriolis correction for a shot fired either N-S at 45 latitude for comparison to the E-W correction you gave? Interesting stuff!
 

WildRose

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Hey Phorwath,

I'm thinking about the Coriolis effect-

In regard to a shot along a North or South trajectory, my gut tells me the target would "move away" from the aim point faster than an East-West shot. I would even be inclined to think a East-West shot (small arms) should have negligible effect because the target is moving almost directly towards or away from the origin of fire.

Can you post a Coriolis correction for a shot fired either N-S at 45 latitude for comparison to the E-W correction you gave? Interesting stuff!
As the graphic I posted shows the target does not remain constant relative to the line of flight of the bullet on such a shot. I've always however been taught that at the ranges we are talking about it's simply negligible.

I'm beginning to wonder if the program he's using calculates some affect on the actual flight of the bullet relative to something akin to centrifugal force which I've not ever considered.

If you think about a spinning ball if you drop a little water on it's top axis the water will naturally gravitate towards the equator and then "spin off" of the ball.

If this is the case I'm actually learning something new for a change because I would have never considered such an effect to have any significance in point of impact.
 

phorwath

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Hey Phorwath,

I'm thinking about the Coriolis effect-

In regard to a shot along a North or South trajectory, my gut tells me the target would "move away" from the aim point faster than an East-West shot. I would even be inclined to think a East-West shot (small arms) should have negligible effect because the target is moving almost directly towards or away from the origin of fire.

Can you post a Coriolis correction for a shot fired either N-S at 45 latitude for comparison to the E-W correction you gave? Interesting stuff!

I thought the same until I spent days researching the topic.

Remember the input parameters here are the OP's 3000 fps MV, and a 200 gr Nosler Accubond bullet with an advertised G1-BC = 0.588.

At 45 degrees North Latitude, the rightward Coriolis Drift is 2.5" at 1000 yds no matter the direction of fire. The horizontal component of Coriolis drift is not dependent on the direction of horizontal fire. You can point your rifle N-S-E-W. NE-SW-NW-SE. The rightward bullet drift due to the Coriolis Effect is 2.5" over the first 1000 yds of bullet travel. Coriolis caused horizontal drift is dependent on Latitude of the shooter, being maximized at the poles and minimized to essentially zero for a shooter at the earth's equator.

Coriolis Drift also causes a vertical component of bullet drift, and the quantity of vertical drift IS dependent on the direction of fire. Vertical drift is maximized with true East and true West directions of fire, and diminishes to zero when the direction of fire is true North or true South. In addition, vertical bullet drift is maximum at the earth's equator, and minimized to basically zero at both poles, even with the directions of fire being due East or due West.
 

phorwath

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I'm beginning to wonder if the program he's using calculates some affect on the actual flight of the bullet relative to something akin to centrifugal force which I've not ever considered.

If you think about a spinning ball if you drop a little water on it's top axis the water will naturally gravitate towards the equator and then "spin off" of the ball.

The centripetal force created due to the earth's rotation is a major force causing Coriolis bullet drift.

Believe me, this is not an easy topic to get your head around. I'm an engineer by training and profession. I've had a lot of math, calculus, differential equations, and even an entry level finite element course(s) in college - but that was many years ago. It took me days of research to come to a reasonable comfort level with my understanding of Coriolis effect-caused bullet drift involving small arms fire. I don't proclaim to be knowledgeable enough to teach it. I believe I understand the phenomena well enough to be able to recognize when I should, and shouldn't, be concerned about adding dope in order to account for Coriolis drift for long range shots.
 
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fatrack

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Phorwath,

So the output from your ballistic program shows the same correction regardless of direction of fire? It is my understanding that programs with a correction for Coriolis have an input for bearing and I would wonder why they have this if it makes no difference on the correction?
 

ken snyder

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Jul 26, 2010
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Twist your scope so that it tracks with the windage, Horizontal level is wrong for your rifle barrel. Leveling off of the action doesn't mean a thing, but is a good place to start.
 

Camshaft

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Jun 14, 2010
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All of this bull **** over a screwy scope, come on now guys, its pretty freaking simple, the scope is a piece of ****, tracking wise, send it back and get a replacement that will dial properly.
 
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