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New ballistics program for Android phones

 
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  #15  
Old 10-25-2010, 09:40 AM
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Re: New ballistics program for Android phones

Quote:
Originally Posted by bsl135 View Post
Trajectory validation as it's commonly thought of usually involves adjusting MV or BC to get the predicted trajectory to match actual. Sometimes MV and BC might be the correct variables to alter, but in my experience, often times the culprit is scope adjustment.

Example; A program predicts 30 MOA of drop. You dial it, hit high, and go about modifying MV or BC in the program until predicted matches observed. But did you ever check to verify that your scope is moving as you think? Correcting a trajectory based on MV or BC when the real problem is scope adjustment gives you the illusion that you're solving the problem, but what you end up with is a solution that's really only correct for a single range. If you address the real problem, you'll have a solution that's more accurate for all ranges.

Shooter has a variable called correction factor, which is a multiplier you can apply to your sight adjustment so that the program accounts for the error between expected and actual reticule movement.

-Bryan
I never really thought of the error being in the scope adjustment. Although I feel like I remove this variable with three data points rather than just one. My trajectory validation this particular instance was done at 200, 300, and 400 yards for both rifles (If I can, I prefer validation at even longer distances out to 600). The amount of 'error' at each distance was just about the same. So I feel confident that it is not just scope adjustment.

Good to know that Shooter has a 'correction factor'. Can you use multiple data points for this correction?
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  #16  
Old 10-25-2010, 12:17 PM
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Re: New ballistics program for Android phones

Quote:
Originally Posted by bsl135 View Post
Trajectory validation as it's commonly thought of usually involves adjusting MV or BC to get the predicted trajectory to match actual. Sometimes MV and BC might be the correct variables to alter, but in my experience, often times the culprit is scope adjustment.

Example; A program predicts 30 MOA of drop. You dial it, hit high, and go about modifying MV or BC in the program until predicted matches observed. But did you ever check to verify that your scope is moving as you think? Correcting a trajectory based on MV or BC when the real problem is scope adjustment gives you the illusion that you're solving the problem, but what you end up with is a solution that's really only correct for a single range. If you address the real problem, you'll have a solution that's more accurate for all ranges.

Shooter has a variable called correction factor, which is a multiplier you can apply to your sight adjustment so that the program accounts for the error between expected and actual reticule movement.

-Bryan
Bryan How do I get to that correction your talking about?
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  #17  
Old 12-01-2010, 03:08 PM
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Re: New ballistics program for Android phones

Yes, Brian. how do you accomplish that correction. This would be a great help.

Matt
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  #18  
Old 12-01-2010, 04:06 PM
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Re: New ballistics program for Android phones

When you are creating a new firearm profile, the is an option called correction factor. This means if your Scopes adjustment is .280moa rather than a true .250moa than you would use a correction factor of .030.
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  #19  
Old 12-01-2010, 04:22 PM
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Re: New ballistics program for Android phones

You figure out your correction factor like this:

Shoot a group to your zero at 100 yards (make sure you measure the range exactly).

Then dial the elevation up 20 or 30 MOA (this requires a tall target) and shoot another group.

Measure the actual distance between the group centers.

Divide by the intended movement of the group.

For example, let's say you dialed 20 MOA, and the group moved 25.6" at 100 yards. The group should have moved: 20*1.047 = 20.94". So the POI moved more than it should have. In fact it moved 25.6/20.94 = 1.22 times farther than it should have. In order to correct for the fact that you scope moves more than expected, the correction factor has to be 1/1.22 = .82.

So applying a correction factor of .82 to your turret adjustments will result in an accurate adjustment.

A short-cut would be to divide the intended movement by the actual movement:
20.94/25.6 = .82. I went thru the above process to try and illustrate what the calculation is doing.

Take care,
-Bryan
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  #20  
Old 12-01-2010, 07:06 PM
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Re: New ballistics program for Android phones

I put meter stick at exactly 100 yards and keeping the scope aimed at zero I dial in 36 minutes of elevation. If the scope moves to 36 inches, it is shooter moa. If it moves 37.75 it is true moa (36* 1.047). Any other variation do the math and apply the correction factor in program as described.
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  #21  
Old 12-04-2010, 11:53 AM
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Re: New ballistics program for Android phones

Last week I upgraded phones to a Motorola Droid X and purchased the "Shooter" app. I have been playing with it and really like the fact it is always with me. The Coriolis and spin drift corrections are easy to check and I like the fact that wind is applied in the "Clock" method rather than degrees. I want to further test the accuracy of getting field conditions from the GPS mode, but first impressions are good so far. This program is easy to run and easy for me to understand. I plan to add a bluetooth kestrel to my pack for occations where I have no cell service to access the GPS field conditions. The swithing from GPS to bluetooth is easy to access as well. Another thing I like is the ability to page up or down on the wind speed, direction and distances by a simple touch of the + or - button. The updated corrections come up fast too.

The only thing I wish it had would be the arrows like Bryan showed in the begining post to indicate up and direction of windage correction. My program makes the elevation number in red with a + in front and the windage in green with a + or - behind it. This could prove to be confusing when you add in spin drift and coriolis. Does anyone know if there is a setting to change this so left and right corrections are easier to understand?

Just wanted to give my first impresion and I will follow up with my finding on accuracy in the field.

Jeff
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