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Rifles, Reloading, Optics, Equipment
Reloading
Powders and MV change in cold temps
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<blockquote data-quote="Kevin Thomas" data-source="post: 491078" data-attributes="member: 15748"><p>Schoeneck,</p><p> </p><p>All powders are temperature sensitive to some degree, with some being better than others. The basic rule for IMR series powders (and most similar single based extruded powders) is roughly 1.7 fps per degree of change. That is, a 30 degree change in temp will give a change in velocity of about 50 fps. The higher the temp, the higher velocity (and pressure), the lower the temp, the lower, etc..While some of the newer powders are being improved in this regard, they all have some sensitivity to air temp, no way around that. Ball powders tend to be a bit worse in this regard, but even they are still stable enough for military usage. I don't recall the exact range they go to, but Lake City Army Ammunition plant does test firings with ammo that's held in an oven for a period of hours (24?), but I want to say it's like 140 degrees? Could be more. They also freeze it down to about 60 below zero. The ammunition has to pass at both extremes, with pressure neither rising nor falling below set limits, and velocities not deviating beyond specific ranges. Pretty tough test.</p></blockquote><p></p>
[QUOTE="Kevin Thomas, post: 491078, member: 15748"] Schoeneck, All powders are temperature sensitive to some degree, with some being better than others. The basic rule for IMR series powders (and most similar single based extruded powders) is roughly 1.7 fps per degree of change. That is, a 30 degree change in temp will give a change in velocity of about 50 fps. The higher the temp, the higher velocity (and pressure), the lower the temp, the lower, etc..While some of the newer powders are being improved in this regard, they all have some sensitivity to air temp, no way around that. Ball powders tend to be a bit worse in this regard, but even they are still stable enough for military usage. I don't recall the exact range they go to, but Lake City Army Ammunition plant does test firings with ammo that's held in an oven for a period of hours (24?), but I want to say it's like 140 degrees? Could be more. They also freeze it down to about 60 below zero. The ammunition has to pass at both extremes, with pressure neither rising nor falling below set limits, and velocities not deviating beyond specific ranges. Pretty tough test. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Powders and MV change in cold temps
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