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Long Range shots - elevation right on always to the right

 
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  #29  
Old 08-25-2011, 02:31 AM
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Re: Long Range shots - elevation right on always to the right

Quote:
Originally Posted by phorwath View Post
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.
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  #30  
Old 08-25-2011, 02:33 AM
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Re: Long Range shots - elevation right on always to the right

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Originally Posted by phorwath View Post
... .Some consider 8.8 inches both measurable and significant.
If we were discussing a mile shot, then 8.8 inches would be worthy of note and discussion.

We're however not.

We are working at much shorter distances.
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  #31  
Old 08-25-2011, 03:42 AM
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Re: Long Range shots - elevation right on always to the right

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Originally Posted by WildRose View Post
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...

Last edited by phorwath; 08-25-2011 at 12:46 PM.
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  #32  
Old 08-25-2011, 08:47 AM
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Re: Long Range shots - elevation right on always to the right

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.
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  #33  
Old 08-25-2011, 08:55 AM
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Re: Long Range shots - elevation right on always to the right

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Originally Posted by WildRose View Post
I'd say go ahead and correct for your 400yd windage and get it dead on there.

Then bring it in to 100yds and see where you are.

If you're still dead on at 100, then something's fishy..

It almost makes me think your scope is mounted with a twist/yaw right to left.
x2. Good luck.
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  #34  
Old 08-25-2011, 09:33 AM
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Re: Long Range shots - elevation right on always to the right

I believe wildrose is correct ,,he is not launching motar rounds or artillery.
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  #35  
Old 08-25-2011, 10:45 AM
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Re: Long Range shots - elevation right on always to the right

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!
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