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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Altitude vs. Barometric pressure
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<blockquote data-quote="User4302021" data-source="post: 1508950" data-attributes="member: 105322"><p>This thread has some long legs...it's 13+ years from the OP. This isn't aimed at any poster, just general info.</p><p></p><p>The difference between Station Pressure and Barometric Pressure needs to be understood to do this correctly.</p><p></p><p>At any given location, station pressure doesn't change enough from day to day... much less throughout a single day... to make a difference at distances from 1000 yards and closer. </p><p></p><p>The higher you are in altitude, the less difference it makes anyway, because your bullet is flying with ever increasing efficiency as altitude increases.</p><p></p><p>You could literally look at a topo map, put in the standard pressure for that altitude and be perfectly fine. Or, you could just wear a G-Shock watch that gives station pressure without spending $600 on an Applied Ballistics Kestrel.</p><p></p><p>If you don't know how temperature effects your powder burn rate for your cartridge then a AB Kestrel won't help you there either because it will be guessing for you. But, 0.7 fps per 1 degree ambient temp is a pretty good average. A simple keychain thermometer will get you more than close enough to actual temp for these purposes.</p><p></p><p>You can literally plug in all this basic stuff into JBM Ballistics for free before you leave the house, write it down, and be perfectly fine. It doesn't need to be complicated.</p></blockquote><p></p>
[QUOTE="User4302021, post: 1508950, member: 105322"] This thread has some long legs...it's 13+ years from the OP. This isn't aimed at any poster, just general info. The difference between Station Pressure and Barometric Pressure needs to be understood to do this correctly. At any given location, station pressure doesn't change enough from day to day... much less throughout a single day... to make a difference at distances from 1000 yards and closer. The higher you are in altitude, the less difference it makes anyway, because your bullet is flying with ever increasing efficiency as altitude increases. You could literally look at a topo map, put in the standard pressure for that altitude and be perfectly fine. Or, you could just wear a G-Shock watch that gives station pressure without spending $600 on an Applied Ballistics Kestrel. If you don't know how temperature effects your powder burn rate for your cartridge then a AB Kestrel won't help you there either because it will be guessing for you. But, 0.7 fps per 1 degree ambient temp is a pretty good average. A simple keychain thermometer will get you more than close enough to actual temp for these purposes. You can literally plug in all this basic stuff into JBM Ballistics for free before you leave the house, write it down, and be perfectly fine. It doesn't need to be complicated. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Altitude vs. Barometric pressure
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