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Long Range shots - elevation right on always to the right

 
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  #22  
Old 08-25-2011, 12:13 AM
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Re: Long Range shots - elevation right on always to the right

Quote:
Originally Posted by phorwath View Post
My last effort to assist:

I just analyzed your bullet and load using Patagonia Ballistics LoadBase3.0 ballistics software.
Spin Drift: Input Parameters
200 gr Nosler Accubond
3000 fps
G1 BC=0.588
Bullet length=1.49"
10:1 rifling twist rate
Rifle Zero Point = 100 yds
Environmental Conditions= ICAO Standard Conditions.

Spin Drift at 1000 yds = 6.6 inches rightward drift from right twist rifled barrel

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
Combined, a total of 9.1 inches of rightward drift at 1000 yds

Do as you will with Spin Drift and Coriolis Drift. You can throw them out with the trash and keep re-mounting your scope until you've stripped the base and ring screws free of any remaining threads. But this isn't witchcraft, and you'll never rid yourself of these two sources of bullet drift.

With respect to the prior Post: 1000 yds is a lot less than one mile. I can measure 2.5 inches of Coriolis Drift on target without a magnifying glass. I consider 2.5 inches of 'known' drift to be a measurable effect on my predictive 1000 yard dope.

For the curious... At a distance of one mile there would be 8.8 inches of Coriolis caused rightward drift. Spin Drift is 33.4 inches at one mile.
Only if the shots are fired on a direct N-S Axis.

With respect to my prior post, let me correct myself.

Significant rather than measurable. I realize you can measure just about anything these days.

2.5" isn't enough to miss a 1000yds shot on a jackrabbit so I don't consider it to be significant.
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  #23  
Old 08-25-2011, 01:02 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
Only if the shots are fired on a direct N-S Axis.

With respect to my prior post, let me correct myself.

Significant rather than measurable. I realize you can measure just about anything these days.

2.5" isn't enough to miss a 1000yds shot on a jackrabbit so I don't consider it to be significant.
You'll have to explain yourself with respect to "Only if the shots are fired on the direct N-S Axis." I've gotta presume you're talking about Coriolis Drift. And I've gotta presume you're of the belief that magnetic directions of fire are the correct parameters to input to calculate the magnitude of Coriolis Drift, based on your recommendation to NVH1 to "Take a compass out to where you are shooting, and shoot a line to Magnetic North."

If so, you are misinformed on both accounts, and you're providing errant information, advice, and commentary.

Firstly, the correct direction of fire for purposes of calculating Coriolis Drift is not the magnetic direction. It's the magnetic direction corrected by the quantity of the earth's magnetic declination at the shooter's location on the surface of the earth. In other words, the magnetic Azimuth of fire must be corrected by the quantity of earth's magnetic declination in order to obtain the true Azimuth of fire. Where I hunt in Alaska, the earth's magnetic declination is 20 degrees east. So if, as you suggested, I set up my target 1000 yds magnetically due north from my position of fire, the actual (corrected) direction (Azimuth) of fire would end up being 20 degrees west of True North, for an Azimuth of 340 degrees. The use of magnetic Azimuth's will result in erroneous calculations of Coriolis Drift.

Secondly, the magnitude of the horizontal component of Coriolis Drift is essentially the same whether the Azimuth of fire is true North (0 degrees), true South (180 degrees), true East (90 degrees) or true West (270 degrees) from any specific Latitude on the earths surface. And the horizontal Coriolis Drift is essentially zero at the equator for small arms fire, regardless of the Azimuth of fire, and maximized at the north and south poles. My prior calculations were based on a location at 45 Degrees North Latitude - half way from the earth's equator to the north pole.

Lastly, and this may hurt..., but 8.8 inches of horizontal Coriolis Drift at 1 mile is neither not measurable, nor insignificant. I only quoted the 2.5 inches at 1000 yards because the original poster was seeking to identify the cause of rightward horizontal bullet drift at 1000 yards. But you did state your contention that "the Coriolis effect is not going to have any measurable effect at ranges of under one mile."

Perhaps you should correct yourself.

Last edited by phorwath; 08-25-2011 at 12:50 PM.
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  #24  
Old 08-25-2011, 01:07 AM
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Re: Long Range shots - elevation right on always to the right

Quote:
Originally Posted by phorwath View Post
You'll have to explain yourself with respect to "Only if the shots are fired on the direct N-S Axis." I've gotta presume you're talking about Coriolis Drift. And I've gotta presume you're of the belief that magnetic directions of fire are the correct parameters to input to calculate the magnitude of Coriolis Drift, based on your recommendation to NVH1 to "Take a compass out to where you are shooting, and shoot a line to Magnetic North."

If so, you are misinformed on both accounts, and you're providing errant information, advice, and commentary.

Firstly, the correct direction of fire for purposes of calculating Coriolis Drift is not the magnetic direction. It's the magnetic direction corrected by the quantity of the earth's magnetic declination at the shooter's location on the surface of the earth. In other words, the magnetic Azimuth of fire must be corrected by the quantity of earth's magnetic declination in order to obtain the true Azimuth of fire. Where I hunt in Alaska, the earth's magnetic declination is 20 degrees east. So if, as you suggested, I set up my target 1000 yds magnetically due north from my position of fire, the actual (corrected) direction (or Azimuth) of fire would end up being 20 degrees west of True North, for an Azimuth of 340 degrees. The use of magnetic Azimuth's will result in erroneous calculations of Coriolis Drift.

Secondly, there is NO horizontal Coriolis Drift when the Azimuth of fire is either true North (0 degrees) or true South (180 degrees). Just the opposite of your contention. Horizontal Coriolis Drift is maximized when the Azimuth of fire is true East or true West. Horizontal Coriolis Drift is zero when the Azimuth of fire is true North or true South. Additionally, horizontal Coriolis Drift is zero at the equator regardless of the Azimuth of fire, and maximized at the north and south poles. My prior calculations were based on a location at 45 Degrees North Latitude - half way from the earth's equator to the north pole.

Lastly, and this may hurt..., but is 8.8 inches of horizontal Coriolis Drift at 1 mile neither measurable nor significant. I only quoted the 2.5 inches at 1000 yards because the original poster was seeking to identify the cause of rightward horizontal bullet drift at 1000 yards. But you did state your contention that "the Coriolis effect is not going to have any measurable effect at ranges of under one mile."

Perhaps you should correct yourself.
You assume incorrectly. It's called getting information one piece at a time.

It's easy to get the declination constant for any given location and then to correct from magnentic north to true north.

http://www.solarpathfinder.com/magnetic

If the shots are not being fired along the north south axis then whatever Corriolis affect corrections are not going to be the same.



If the spin of the bullet is in the opposite direction of the deflection it's an add. If it's with it the correction is subtracted.

If the shots are directly in line with the direction the earth is spinning there is nothing to correct with respect to the Coriolis affect at all. The earth spins on a N-S axis thus the effect is West-East.
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Last edited by WildRose; 08-25-2011 at 02:34 AM. Reason: because sometimes my spelling sucks alot... .
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  #25  
Old 08-25-2011, 01:15 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
... .Perhaps you should correct yourself.
Perhaps if you learn to read you would note that I did.

Quote:
With respect to my prior post, let me correct myself.

Significant rather than measurable.
It is actually possible to have a discussion and disagree without being a snarky smartass.
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  #26  
Old 08-25-2011, 01:26 AM
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Re: Long Range shots - elevation right on always to the right

Yeah. Right. Exactly.

Now you've not only confirmed that you're misinformed, but that you're also too proud to admit your error(s).


For the sake of the OP and the other member's that might be trying to identify a solution to their mysterious rightward drift, would you first become knowledgeable about what it is that you don't know - before trying to help? I contend that amongst the most dangerous of the dangerous, is the person that doesn't know what they don't know.

I'm not going out of my way to bash you. But the information you're spreading is incorrect, false, wrong, untrue. It may seem harmless enough to you, but it could have an adverse affect on other members. Some consider 8.8 inches both measurable and significant.
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  #27  
Old 08-25-2011, 01:30 AM
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Re: Long Range shots - elevation right on always to the right

Quote:
Originally Posted by phorwath View Post
Yeah. Right. Exactly.

Now you've not only confirmed that you're misinformed, but that you're also too proud to admit your error(s).


For the sake of the OP and the other member's that might be trying to identify a solution to their mysterious rightward drift, would you first become knowledgeable about what it is that you don't know - before trying to help? I contend that amongst the most dangerous of the dangerous, is the person that doesn't know what they don't know.

I'm not going out of my way to bash you. But the information you're spreading is incorrect, false, wrong, untrue. It may seem harmless enough to you, but it could have an adverse affect on other members. Some consider 8.8 inches both measurable and significant.
If you wish to go out of your way to be an ass by all means don't let me interrupt.

Like I said, it is possible to have a discussion and even degree without being a jackass; at least for some of us.

I don't consider it to be significant for anything we are shooting.

If I were running the FDC for a mortar squad or artillery I would.

If I were shooting at 2,400m with a .408 or .375, I would think it significant enough to account for.

At these ranges, no I don't.

Of course "significant" is relative... .
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  #28  
Old 08-25-2011, 02:18 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
Perhaps if you learn to read you would note that I did.

It is actually possible to have a discussion and disagree without being a snarky smartass.
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.
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