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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Altitude vs. Barometric pressure
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<blockquote data-quote="JBM" data-source="post: 78470" data-attributes="member: 1969"><p>The real variable here is density. Temperature, pressure and humidity play into it. Temperature and humidity also change the speed of sound which changes the drag (which is a function of mach number, not velocity), but this is less noticable. The problem with using altitude is that you have to assume an atmospheric model an calculate density from it which can be way off. The reason we have these atmospheric models and why altitude plays into it is so that airplane altimeters can be altitude corrected consistently around the world.</p><p></p><p>As for scope height errors, yes it can affect it, but it should be small at close ranges. The kind of error it adds is an angular error so at farther ranges it gets worse.</p></blockquote><p></p>
[QUOTE="JBM, post: 78470, member: 1969"] The real variable here is density. Temperature, pressure and humidity play into it. Temperature and humidity also change the speed of sound which changes the drag (which is a function of mach number, not velocity), but this is less noticable. The problem with using altitude is that you have to assume an atmospheric model an calculate density from it which can be way off. The reason we have these atmospheric models and why altitude plays into it is so that airplane altimeters can be altitude corrected consistently around the world. As for scope height errors, yes it can affect it, but it should be small at close ranges. The kind of error it adds is an angular error so at farther ranges it gets worse. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Altitude vs. Barometric pressure
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