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Rifles, Reloading, Optics, Equipment
Reloading
Temperature and humidity factor - how do they affect my loads?
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<blockquote data-quote="Chawlston" data-source="post: 116219"><p>[ QUOTE ]</p><p>[ QUOTE ]</p><p>Grouping was 1.25" and velocity averaged 3175 fps. Yet the IMR manual states a velocity of 3081 fps for a 60.5 gr load of this same powder. My loads clocked nearly 100 fps faster with 1.5 grain less powder. This must be the obvious results of this temperature differential that we speak of.</p><p></p><p>[/ QUOTE ]I don't think it's local atmospheric conditions. You probably used a different barrel as well as powder lot and maybe a different bullet, primer and case. All of which can easily result in a 100 fps difference from published load data even in identical atmospheric conditions. Plus two people can easily get more than a 50 fps difference shooting the same ammo and rifle from bags atop a bench just because they hold the rifle differently. </p><p></p><p>[/ QUOTE ]</p><p></p><p>Not to mention the differences in chronographs and powder scales. Until I got my Oehler 35P with the three skyscreens along with my acculab scale, I never realized what reapeatabe and verifieable consistency could be acheived. So far, I could have more or less igniored the target and just tuned the load based on shot to shot velocity deviation. Good instruments reveal may secrets.</p><p></p><p>Chawlston</p></blockquote><p></p>
[QUOTE="Chawlston, post: 116219"] [ QUOTE ] [ QUOTE ] Grouping was 1.25" and velocity averaged 3175 fps. Yet the IMR manual states a velocity of 3081 fps for a 60.5 gr load of this same powder. My loads clocked nearly 100 fps faster with 1.5 grain less powder. This must be the obvious results of this temperature differential that we speak of. [/ QUOTE ]I don't think it's local atmospheric conditions. You probably used a different barrel as well as powder lot and maybe a different bullet, primer and case. All of which can easily result in a 100 fps difference from published load data even in identical atmospheric conditions. Plus two people can easily get more than a 50 fps difference shooting the same ammo and rifle from bags atop a bench just because they hold the rifle differently. [/ QUOTE ] Not to mention the differences in chronographs and powder scales. Until I got my Oehler 35P with the three skyscreens along with my acculab scale, I never realized what reapeatabe and verifieable consistency could be acheived. So far, I could have more or less igniored the target and just tuned the load based on shot to shot velocity deviation. Good instruments reveal may secrets. Chawlston [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Temperature and humidity factor - how do they affect my loads?
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