Ranging conundrum

[renegadelzard]

Hey all,

I think im missing something here, so please fix me..here is what is going on. Im building my long range data book and assembling all of the charts and formula's and ive run into a rather strange problem..i have MOA/MOA glass, so using the reticle to range, i have the formula as such

target size in inches x 95.5 / moa measured in reticle...
ive also seen target size in inches/moa measured in reticle x 95.5

both give the same answer..

i also have the ballistic app, and when verifying my answers using the ballistic app rangefinder funtion, i get a different answer

formula:

(72 inches X 95.5)/11moa=625.09 yards

the ballistic app rangefinder calculates it out to 613.9 yards....

Any idea on why this is different? is my formula correct?

Also, using the range as determined by the formula, to calulate the actual horizontal range in yards, i simply multiply the measured range times the cosine of the shooting angle and this will give the actual shooting distance in yards...correct?

 

[FearNoWind]

What's the margin of error for your ballistics calc? You're numbers reflect about 2% .....
Also may be a minor error of interpretation of the subtensions in the scope image. It doesn't take much.

 

[renegadelzard]

What's the margin of error for your ballistics calc?

That is the unknown here i guess...the app is simply called ballistic (used to be called zadarski ballistic), and it proportedly uses the JBM ballistics engine...there is very little documentation on the rangefinder part of the program though.

 

[Bravo 4]

Also, using the range as determined by the formula, to calulate the actual horizontal range in yards, i simply multiply the measured range times the cosine of the shooting angle and this will give the actual shooting distance in yards...correct?

A good read:
Angle Shooting

 

[BergerBoy]

That's strange.... Your formula is correct 95.5 x inches/MOA = distance in yards.
I was always taught that. Maybe your using it and getting distance in meters???

 

[sscoyote]

May be something wrong with the program. Your calc's right. The 95.5 factor is correct (100yds./1.0472"). Weird!

 

[pyroducksx3]

Maybe just get a rangefinder and check. Then after that just use the rangefinder.

 

[bruce_ventura]

I ran the same calculation on the Ballistic app in my iPhone: 72 inch target measuring 11 MOA. I get 625.0 yds. Not exactly correct, but extremely close.

 

[MMERSS]

Is the ballistics application applying inclination to the range resulting in a "shoot to" solution? In other words, is the ballistics application correctly calculating the range based off a known target size then applying an inclination to this range resulting in a "shoot to" range?

 

[renegadelzard]

I thought maybe that was it as well, so I tried it again last night and made sure the cosine indicator was locked at zero, still got the same results. If it was the GUI interface and the substentions on the heads up reticle, I could learn to live with that, but it gives a numerical readout and set to those numbers precisely. This makes me doubt any firing solution now, if the basic formula for range is off, how can I trust the other more esoteric values such as coriolis and spin drift? Anyone using anything else that isn't to expensive and will run on an I phone?