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Hunting
Long Range Hunting & Shooting
Altitude & Temperature Effects on a Bullet?
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<blockquote data-quote="sierra22" data-source="post: 64772" data-attributes="member: 949"><p>Shadowman, my results from freezing the ammo is far from conclusive yet, as I've only done it 4 times to check powder/primer combination.</p><p></p><p>With both VitN150 and Norma MRP powder, I get less velocity drop with Fed large rifle primers, than I do with CCI. Accuracy is equal.</p><p></p><p>With these new "temperature-velocities", I plot them into my ballistic program and see what the it translates to at the various ranges of my dropchart. </p><p></p><p>For example (I don't have my chart in front of me now - -numbers are out of the blue) if I get 820 meters/second at 15C (standard atmosphere) that translates to 51 clicks (I'm a MIL-man so I don't use MOA) at 600 meters. </p><p>Measuring the same ammo at 5C I get 804m/sec which is 55 clicks, or a 4 click deviation. And so on, and so on...</p><p></p><p>All of this comes together like this:</p><p>I'm looking at my ballistic chart which is calculated for standard atmosphere.</p><p>I read 1050hPa and 5Celsius of my Silva Alba weatherstation.</p><p>Standard atmosphere conditions is 1000hPa and 15C (the ballistic chart).</p><p></p><p>"Hmm,range is 600 which is 51clicks. Deviation from SAC is 50hPa and 10Celsius. My chart says at this range says 0,2 clicks per 10 hPa and 0,4 clicks per 5Celsius and +4 for ammo temperature. That is +1 click for hPa and +0,8click for temperature. 51clicks + 1 + 0,8 +4 = 56 clicks corrected.</p><p></p><p>Not 100% accurate, but a lot more than not doing it, or so it seems.</p></blockquote><p></p>
[QUOTE="sierra22, post: 64772, member: 949"] Shadowman, my results from freezing the ammo is far from conclusive yet, as I've only done it 4 times to check powder/primer combination. With both VitN150 and Norma MRP powder, I get less velocity drop with Fed large rifle primers, than I do with CCI. Accuracy is equal. With these new "temperature-velocities", I plot them into my ballistic program and see what the it translates to at the various ranges of my dropchart. For example (I don't have my chart in front of me now - -numbers are out of the blue) if I get 820 meters/second at 15C (standard atmosphere) that translates to 51 clicks (I'm a MIL-man so I don't use MOA) at 600 meters. Measuring the same ammo at 5C I get 804m/sec which is 55 clicks, or a 4 click deviation. And so on, and so on... All of this comes together like this: I'm looking at my ballistic chart which is calculated for standard atmosphere. I read 1050hPa and 5Celsius of my Silva Alba weatherstation. Standard atmosphere conditions is 1000hPa and 15C (the ballistic chart). "Hmm,range is 600 which is 51clicks. Deviation from SAC is 50hPa and 10Celsius. My chart says at this range says 0,2 clicks per 10 hPa and 0,4 clicks per 5Celsius and +4 for ammo temperature. That is +1 click for hPa and +0,8click for temperature. 51clicks + 1 + 0,8 +4 = 56 clicks corrected. Not 100% accurate, but a lot more than not doing it, or so it seems. [/QUOTE]
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