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Finally went beyond 1000 yards

 
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  #8  
Old 03-01-2013, 03:02 PM
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Re: Finally went beyond 1000 yards

The first wind has the greatest effect on the bullet path. The first wind starts the trajectory off path earlier and it will continue off path from point of aim / to point of impact growing with distance. The last wind drift the bullet encounters will have the least effect. Drift is an equivalent to BC. I have actually seen bullets gain BC as they slow. I do not feel there is a given that a bullet has to loose BC as it slows.

Jeff
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Old 03-01-2013, 03:12 PM
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Re: Finally went beyond 1000 yards

Interesting. That is the opposite of what I was taught. For example if you shoot 1000 yards. Break it down to first 500 and second 500. The bullet travels the first 500 quicker and is less effected by the wind due less flight time. The bullet is effected more during the second half as it takes longer to travel the same distance.

Good info though. Need to test the shots on each side of gully I guess. LOL.
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Old 03-01-2013, 03:22 PM
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Re: Finally went beyond 1000 yards

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Originally Posted by BrentM View Post
Interesting. That is the opposite of what I was taught. For example if you shoot 1000 yards. Break it down to first 500 and second 500. The bullet travels the first 500 quicker and is less effected by the wind due less flight time. The bullet is effected more during the second half as it takes longer to travel the same distance.

Good info though. Need to test the shots on each side of gully I guess. LOL.
Imagine a "V" The sooner the bullet starts off path the greater it will be from point of aim. If there is no wind at the gun and a wind drift starts at the 1/2 way mark the distance from point of aim will be less than if it started earlier. Once the course of flight is upset the distances keeps increasing. The earlier it starts the greater it will be as distance increases.

Jeff
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Old 03-01-2013, 03:25 PM
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Re: Finally went beyond 1000 yards

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Originally Posted by BrentM View Post
Interesting. That is the opposite of what I was taught. For example if you shoot 1000 yards. Break it down to first 500 and second 500. The bullet travels the first 500 quicker and is less effected by the wind due less flight time. The bullet is effected more during the second half as it takes longer to travel the same distance.

Good info though. Need to test the shots on each side of gully I guess. LOL.
While Broz and I may weight things differently for wind variance he's got a solid point.

Any error over the first hundred yards is going to double or close to it with each hundred yards traveled.

As far as changing BC's the more streamlined the bullet (VLD's vs "hunting bullets")the more stable it is at high velocity and the more problems it's going to have as it approaches transonic. It's the same reason we had so many problems with our early supersonic fighter programs since many of them became extremely unstable as they slowed down and were bears to control at best at sub sonic speeds.

Broz and I may not always agree on how to get things done, but we're both very good at getting the job done so his input is always well worth considering. Hell even I learn something from him once in a while. The list of people I truly respect and admire is pretty short and he's on it.
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Old 03-01-2013, 03:49 PM
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Re: Finally went beyond 1000 yards

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Originally Posted by Broz View Post
The first wind has the greatest effect on the bullet path. The first wind starts the trajectory off path earlier and it will continue off path from point of aim / to point of impact growing with distance. The last wind drift the bullet encounters will have the least effect. Drift is an equivalent to BC. I have actually seen bullets gain BC as they slow. I do not feel there is a given that a bullet has to loose BC as it slows.

Jeff
My general experience on the latter point is actually similar.

More or less what I see is that the flat and more rounded nosed bullets gain BC as they slow but that the longer more pointed bullets tend to lose it and the more pointed and streamlined the bullet the more rapid the BC deterioration occurs.

It's also generally seemed to me that the wind has a greater effect at longer ranges which tends to be proved out with the ballistic data.

If you take a given bullet and plot it's wind corrections across a 1,000yds shot by breaking the shot into three separate shots using the calculated velocities at MV-330, 330-660, and 660-1,000 I think with most bullets we use you'll see what I mean.


The following table is provided as a "cheat sheet" that you can tape to your gun.

Your Round 180 gr. 0.5 B.C.
Range Muzzle3006009001200
Trajectory -1.5-9.2-62.9-187.2-424.5
Come UP in MOA 02.91019.933.8
Come UP in Mils 00.82.95.89.8
Wind Drift 05.222.757114.1
Wind Drift in MOA 01.63.66.19.1
Wind Drift in Mils 00.51.11.82.6
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  #13  
Old 03-01-2013, 04:10 PM
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Re: Finally went beyond 1000 yards

I see your point regarding the initial movement of the bullet and how it is effected down range. Similar to flinching, pushing, jerking the trigger, a little at the muzzle is a lot at the target and it becomes greater with distance.

This video is how I was taught by the same instruction standards. However, I do believe you have valid points and all these things add up.

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  #14  
Old 03-01-2013, 04:12 PM
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Re: Finally went beyond 1000 yards

Question for you experienced guys out there. Is wind drift affected by B.C. in that the lower the B.C. the faster the bullet slows down and the longer it is in flight being affected by the wind?

For example, could drift be calculated by the mass of the bullet and it's time of flight, or is there something to the shape of the bullet as well?

Case in point, if you had two bullets of the same shape / weight, but one (somehow) had a lower B.C. would they have the same amount of drift at the same time in flight. Even though the lesser B.C. bullet would not have carried as far due to velocity loss?

Thanks (if you followed all of that),
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