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Incline shooting at ELR, Apps give different results?

 
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  #8  
Old 09-22-2012, 04:05 PM
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Re: Incline shooting at ELR, Apps give different results?

I built a ballistics app from scratch while working for a defense contractor and found that getting the correct result for inclined shots was not easy. The geometry is not easy to follow through with and you need to make adjustments based on the standard models of the atmosphere for air density to get a sound solution.

The poster who was talking about an absolute science and how that should make ballistics solutions match reality all the time should keep in mind that the atmospherics that you punch in even based upon at muzzle measurements are not "exactly" constant over the path of the bullet. The easiest one to visualize is the wind, it is not constant over the path of the projectile. Without a system that can measure the wind between the muzzle and the target you are making at best estimations of the wind along the path. There are system that can measure the wind profile, Google Lockheed Martin OneShot for one example, but they are expensive maybe heavy etc. that currently make them impractical for hunting.
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  #9  
Old 09-24-2012, 11:10 PM
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Re: Incline shooting at ELR, Apps give different results?

I hope you don't mind me intruding, but I had a similar post you might find interesting. Everyone knows, when shooting uphill or downhill, the shooter is required to use less hold-over, correct? Now, enter 5.9 and -5.9 for the incline using your 2000m shot. The difference grows at longer ranges,but both ShooterFTE and Bulletflight agree that the downhill shot will drop more. I think an answer to this would relieve both our concerns. (By the way, Brian, thanks for a great book. I am excited for more.)
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  #10  
Old 09-25-2012, 02:33 AM
M67 M67 is offline
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Re: Incline shooting at ELR, Apps give different results?

ajhardle,

Gravity is the reason that a bullet drops more when shooting uphill than downhill. I can throw a rock farther downhill than uphill right?
This is generally not seen when shooting, hardly even in archery, since the kinetic energy of a bullet is far, far greater than the potential energy change due to the bullet travelling up or down - unless at silly distances and steep inclines...

My question was concerning the fact that Bulletflight predicted a much bigger difference between look-up and look-down shots than Shooter.

As one solution had to be (more) wrong i wondered which, and why.

I suspected, and Brian and Robert Silvers, (and Jonathan Zdziarski) confirmed that the difference is due to Shooter correcting for the changing air density (and thus changing drag) along the trajectory. I can only assume this correction is based on the ICAO std. atmosphere and it cannot be valid under all circumstances, but still is far better tha doing no correction at all.

Thus the result Shooter presents is very close to what actual firing will, and in fact does, confirm.


K

Last edited by M67; 09-25-2012 at 04:37 AM. Reason: typos
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  #11  
Old 09-25-2012, 07:52 AM
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Re: Incline shooting at ELR, Apps give different results?

I'm sorry I had written that post incorrectly. The difference was between 5.9 and flat I wanted to point out, and the fact that the uphill shot drops more than no incline. Is it as simple as throwing a rock uphill as opposed to horizontally?
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  #12  
Old 09-26-2012, 10:24 PM
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Re: Incline shooting at ELR, Apps give different results?

[QUOTE=ajhardle;699446] Now, enter 5.9 and -5.9 for the incline using your 2000m shot. The difference grows at longer ranges,but both ShooterFTE and Bulletflight agree that the downhill shot will drop more.




If i was paying attention, I would have realized Litz answered my question, also. I stated Shooter and Bulletflight agree. They don't. Bulletflight and BallisticFTE agree that the uphill shot drops more. Shooter and Applied Ballistics tell us the flat look angle has the most drop, (I could create trajectories that show a small increase in drop for small uphill angles, but we would be talking inches at 2000m).

So what we have is two programs that account for only gravity affecting the incline angle, and two programs acounting both gravity and air density variations, I think.

Let me give an example. ( I will use 2500m and a 9 degree uphill to exaggerate the results).

Using m67's 338 at 2500m, bulletflight predicts 4695" of drop. Move to a target so it is a 9 degree line of sight, and it predicts 4721". 26" more holdover.

Shooter predicts 4693" level and 4665" for 9 degrees. 28" less holdover.

A 2" difference grew to 56" with only a nine degree incline.

In reality, any of the programs are good enough for most shooters. I certainly don't expect a first round hit at 2000m.
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  #13  
Old 09-27-2012, 08:08 AM
M67 M67 is offline
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Re: Incline shooting at ELR, Apps give different results?

Quote:
I certainly don't expect a first round hit at 2000m.
As much as i agree, i think what we have learned here is very good info. And some people actually come very close. Over the years, i have been constantly adjusting my view of what is possible - who knows what we will see in the future.
While you may not expect a first round hit (or even a hit at all...), judging wind at 2km is at best a dicey proposition.
But using a solution that lacks the corrections neccesary, makes certain that you will not hit. It moves the most probable impact point from your target and to somewhere else.
The difference in the solutions in my example is so different that a miss of the same proportion, quite probably would result in what i call a "lost" shot, it would hit where it may not be detected by the spotter(s)

This video by forum member Yrcan show the level of accuracy that can be obtained at 2km.

K
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