I have a few questions about the Applied Ballistics App and how it calculates as well as recommendations for making DOPE cards.
Here it goes. In preferences the AB app is set to use Density Altitude to calculate. (I read somewhere that a 2500 DA calculated with one set of data is different than shooting in a 2500 DA using a different set of data. i.e. low altitude and high temp vs high altitude and low temp. Is this true?) Anyway, I'm setting my target distance to 1,000 yards with 0 wind coming in at 3 O'clock. Selecting the gun and then the bullet, I get to the Environment Screen.
Distance - 1,000 yards
DA defaults to 0 ft
Temperature defaults to 59F
Wind Speed is 0 mph.
This results in U8.1 mils in elevation. If I change the temperature to 0F, the elevation adjustment changes to U8.6 mils.
If DA is a calculation that is in part based on Temperature, then a change in temperature should change the DA. My guess is the DA isn't auto-updating when temperature is changed?
So the question is this. If I'm inputting the DA from a Kestral Sportsman, do I need to adjust the temperature in the AB app as well to get a proper firing solution?
The second half of my thread is regarding making DOPE cards and accounting for spin drift.
Again, using the AB app. Distance is set to 1,000 yards, DA = 0 ft, and Temp = 0F. With 0 wind and spin drift enabled, I need to adjust windage L.02 at a 1,000 yards. My assumption is that at 1,000 yards with the above environmentals, 0.2 mils of adjustment is required to account for spin drift. Lets mix it up. All things being the same except if I add a 10mph wind at 90 degrees, and turn OFF spin drift, the correction for a 90 degree wind is R2.1 mils. The adjustment for an opposing 10 mph wind at a 270 degree angle is the exact same at L2.1 mils. Time to make it interesting. If I turn ON spin drift, a 10 mph wind at 90 degrees requires a correction of R1.9 mils. However, a 10 mph wind at 270 degrees requires a correction of L2.2! So with spin drift turned on, it makes sense that a 90 degree wind would go from R2.1 to R1.9, a 0.2 adjustment, exactly what is called for when accounting for spin drift in a zero wind condition. However, with a 270 degree wind, the adjustment for spin drift is only 0.1 mils. Is this correct? I would think the correction for a 270 degree wind would be L2.3, to mirror the adjustment for spin drift in a zero wind condition.
I'm making DOPE cards based on DA with a low wind value and a high wind value of 5 mph and high of 10mph. I color coded the cells light blue to notate a 0.1 shift for spin drift for each applicable distance, and color coded cells light green for cells corresponding to a distance that requires a 0.2 shift for spin drift. But if I use this logic at 1,000 yards with a 10 mph wind at 270 degrees and apply a 0.2 shift in POI, then I will be 0.1 mils too far left compared to what the ballistics calculator spits out. Which is correct.
And finally! When making a wind call, when do I apply an adjustment for spin drift. Before or after I've corrected for wind angle?
For example. 1,000 yards with a 10mph wind coming in at 45 dgrees. The correction for a 90 degree 10 mph wind with NO spin drift calculated is R2.1. The coefficient for a 45 degree wind is .71, and the adjustment for spin drift is L0.2 mils. So the math can be done one of two ways. Account for spin drift THEN mulitply that number by the angle coefficient, or multiply the wind adjustment by the angle coefficient, THEN apply the correction for spin drift. The math is as follows, which is correct.
(R2.1 + L.02)*.71 = R1.349
or
(R2.1*.71)+L0.2 = R1.291
I know this is splitting hairs and equates to a 1.8" difference in POI. But theoretically, which is correct.
Here it goes. In preferences the AB app is set to use Density Altitude to calculate. (I read somewhere that a 2500 DA calculated with one set of data is different than shooting in a 2500 DA using a different set of data. i.e. low altitude and high temp vs high altitude and low temp. Is this true?) Anyway, I'm setting my target distance to 1,000 yards with 0 wind coming in at 3 O'clock. Selecting the gun and then the bullet, I get to the Environment Screen.
Distance - 1,000 yards
DA defaults to 0 ft
Temperature defaults to 59F
Wind Speed is 0 mph.
This results in U8.1 mils in elevation. If I change the temperature to 0F, the elevation adjustment changes to U8.6 mils.
If DA is a calculation that is in part based on Temperature, then a change in temperature should change the DA. My guess is the DA isn't auto-updating when temperature is changed?
So the question is this. If I'm inputting the DA from a Kestral Sportsman, do I need to adjust the temperature in the AB app as well to get a proper firing solution?
The second half of my thread is regarding making DOPE cards and accounting for spin drift.
Again, using the AB app. Distance is set to 1,000 yards, DA = 0 ft, and Temp = 0F. With 0 wind and spin drift enabled, I need to adjust windage L.02 at a 1,000 yards. My assumption is that at 1,000 yards with the above environmentals, 0.2 mils of adjustment is required to account for spin drift. Lets mix it up. All things being the same except if I add a 10mph wind at 90 degrees, and turn OFF spin drift, the correction for a 90 degree wind is R2.1 mils. The adjustment for an opposing 10 mph wind at a 270 degree angle is the exact same at L2.1 mils. Time to make it interesting. If I turn ON spin drift, a 10 mph wind at 90 degrees requires a correction of R1.9 mils. However, a 10 mph wind at 270 degrees requires a correction of L2.2! So with spin drift turned on, it makes sense that a 90 degree wind would go from R2.1 to R1.9, a 0.2 adjustment, exactly what is called for when accounting for spin drift in a zero wind condition. However, with a 270 degree wind, the adjustment for spin drift is only 0.1 mils. Is this correct? I would think the correction for a 270 degree wind would be L2.3, to mirror the adjustment for spin drift in a zero wind condition.
I'm making DOPE cards based on DA with a low wind value and a high wind value of 5 mph and high of 10mph. I color coded the cells light blue to notate a 0.1 shift for spin drift for each applicable distance, and color coded cells light green for cells corresponding to a distance that requires a 0.2 shift for spin drift. But if I use this logic at 1,000 yards with a 10 mph wind at 270 degrees and apply a 0.2 shift in POI, then I will be 0.1 mils too far left compared to what the ballistics calculator spits out. Which is correct.
And finally! When making a wind call, when do I apply an adjustment for spin drift. Before or after I've corrected for wind angle?
For example. 1,000 yards with a 10mph wind coming in at 45 dgrees. The correction for a 90 degree 10 mph wind with NO spin drift calculated is R2.1. The coefficient for a 45 degree wind is .71, and the adjustment for spin drift is L0.2 mils. So the math can be done one of two ways. Account for spin drift THEN mulitply that number by the angle coefficient, or multiply the wind adjustment by the angle coefficient, THEN apply the correction for spin drift. The math is as follows, which is correct.
(R2.1 + L.02)*.71 = R1.349
or
(R2.1*.71)+L0.2 = R1.291
I know this is splitting hairs and equates to a 1.8" difference in POI. But theoretically, which is correct.