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Elevation and ballistics

 
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Old 10-21-2003, 08:49 AM
700 700 is offline
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Join Date: Jun 2002
Location: Ireland
Posts: 138
Re: Elevation and ballistics

Brent

You are quite wright about the +0.28 MOA measurment. I rechecked and found I misread the altitude correction. It should have been +0.028MOA altitude correction at 100 yards. Then add the -0.006 MOA temperature adjustment and I get +0.022 MOA. Read + as point of impact moves higher. That is pretty close to what you have.

How embarrasing!


A few other differences between our calculations are:

1) You are using Army Metro where as I am using ICAO with a 78% Humidity adjustment added in.
2) I used the 3 ballistic coefficients of
.505 @ 2800 fps and above
.496 between 2800 and 1800 fps
.485 @ 1800 fps and below
quoted on Sierras web site.


.496 is applicable to this cartridge out to about 500 yards.

3) Although generated by software, the charts I was referancing are paper charts and so not as accurate as typing parameters into a dialog box and hittig the OK button.

The charts take a basezero at sealevel and show how in turn altitude , temperature, humidity about that base zero affects the tradjectory. When these variations are taken in concert the charts can only give a rough approximation. But they work pretty good.

Brent,thanks for taking the time to check the calculations and point out my error.


Rgds

700
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