# Whole new Ballistics algorithm

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by ColoYooper, Feb 18, 2013.

1. ### ColoYooperWell-Known Member

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53
Joined:
Feb 17, 2013
My typical method of using current ballistics programs for a new load is to:
1) Lookup the published BC for that bullet
2) Go to the range and zero my scope at 100yrds and record Muzzle Velocity.
3) Use some ballistics calculator and determine 500 yard MOA setting.
4) Shoot at 500 yards and note actual MOA setting (which is different)
5) Use some ballistics calculator and determine 1000 yard MOA setting.
6) Shoot at 1000 yards and note actual MOA setting (which is different)
7) Play with Ballistic calculator and find BC that comes closest to observed 500 and 1000 yard actual for my muzzle velocity.
8) Use ballistics calculator to determine 1200 yard MOA setting using newly determined BC. Guess what. THE BULLET GROUPS LOW.

So what have we figured out. The published BC is a good place to start, but will need refining. And in most cases, the BC will decay as velocity decreases (as is pointed out in the Sierra Manual) So no one G1 or G7 BC curve is going to produce great results at 300, 600, 900 and 1200 yards.

So wrote my own Ballistics Calculator which is attached. This utilizes the steps I normally take anyway. You zero the rifle at 100 yards and enter the Muzzle Velocity: V0. You enter a Mid-Range distance in yards, and the MOA adjustment needed to center your group at the Mid-Range. Ideally the Mid-Range will be in the middle range of your rifles expected use. I like 500 to 600 yards. Then you enter a Long-Range distance in yards, and the MOA adjustment needed to center your group at that range. Again I like 1000 yards, but it should be toward the longer end of the use spectrum. That's it. Then just hit the GO FIGURE button. The program will output 3 important numbers: 1) the V0 muzzle velocity you entered, 2) The Vx Velocity. This would be the 100 yard velocity on the G1 or G7 curve with no BC decay. 3) The VS_SF. This is the amount the application decays the BC for each iteration. This number will be something between 99 which is no decay...to 50 which is a lot of decay. NOTE: Internally the VS_SF numbers are preceded by (5) 9s, so VS_SF of 63 is internally 0.9999963. The program then outputs expected MOA settings for various ranges on the right. You can then enter your current range and hit GO FIGURE and see the computed MOA. You can also enter the wind speed in MPH and a wind direction in clock cordinates (1..12) and see the holdoff in MILS for wind. Anyway this is early in development and I haven't written the Smart Phone App for it yet. Also in development is a Virtual Spotter, which includes this App, but also steams HD Video with a 3 second delay, from a 50x Camera to a tablet. This allows you to take the shot, and then look over at the display and see the hit or miss, with an image of your scopes crosshairs superimposed on the streaming image, and the needed holdoff required to hit the target.

Note: I spent 25 years developing Inertial Navigation systems for the Air Force and currently design Micro Processors.

2. ### M1AShooterActive Member

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27
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Nov 30, 2012
Sounds like your approach is very straight forward, and I'm sure the end result will be very useful & successful. Please keep us posted on development and availability!

3. ### Joe KingWell-Known Member

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1,390
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Apr 29, 2012
Sounds good, but its dependent your chrono being 100% accurate which can be a crap shoot unless you have a very high end unit. When ever you get it fully worked out i expect it'll turn out to be a great tool

4. ### ColoYooperWell-Known Member

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53
Joined:
Feb 17, 2013
I apologize for not being able to attach the .exe program...I'd like some other people to play with it and provide input. The VirtualSpotter HD video streaming program also reads a configuration file that identifies you and the gun, your scope mounting height, the type of crosshairs you have, and whether you want MOA or MILS. But I have managed to attach a couple of screen captures of the simplified VS_Calculator app. Note: It also provides MIL holdoff for entered wind conditions, a vMOA for the bullet drop at the selected yardage, and an hMOA for spin drift at the selected yardage.
Actually, I do see a minor difference of 0.25MOA at the 300yard estimate between the (2) samples...This is due to the application finding 2 differernt G curves and bending them at different decay rates (93 vs 91) to intersect the observed MOA settings at 550 and 1035 yards. But as you can see in the data, variations in measured v0 velocity do not significantly modify the results.

#### Attached Files:

• ###### VirtualSpotter_Examples.bmp
File size:
2 MB
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0
Last edited: Feb 19, 2013