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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
n570 temperature stability
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<blockquote data-quote="Veteran" data-source="post: 2317072" data-attributes="member: 118038"><p>Here's the thing</p><p>......I don't generally like the freeze test though in this specific case it may be informative where going from hotter to cooler or cold climate and you are most worried about loss in velocity.</p><p></p><p>The issue I have w freeze test is when one develops a hot max velocity pressure load in moderate weather and then tries to use it in very hot weather. I think that freeze test is then useless in that case. Because when a load is a hairs breadth from 65,000 psi at 70 degrees and you take it to 100 degrees, and you think your powder is "insensitive" cause you did a freeze test, I hope you have unlimited surgical insurance and a reputable life insurer.......because IMHO losing speed and pressure in cold weather aint the same fps gain in the hot direction. The closer your load is to "rifle scrap metal" </p><p>at 70 degrees, it becomes a bomb at 100. The response curve for burn rate vs. temp may be somewhat linear over reasonable temp. ranges at reasonable charge weights.</p><p></p><p>But once you get out on the limb, that curve becomes exponential on the margin, and it will either surprise you or hurt you. Just my opinion. Ie, hot loads taken into hot weather will act bizarro world.</p><p></p><p>Hot loads taken into cold weather Arent a safety issue, but more of a hunting accuracy and performance issue.</p><p></p><p>Like Clint Eastwood says, a man has gotta know his powder's limitations......<img class="smilie smilie--emoji" loading="lazy" alt="🙂" title="Slightly smiling face :slight_smile:" src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f642.png" data-shortname=":slight_smile:" /><img class="smilie smilie--emoji" loading="lazy" alt="🤔" title="Thinking face :thinking:" src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f914.png" data-shortname=":thinking:" /></p><p></p><p>Burn rates are not a constant!</p><p></p><p>They are not even very consistent from one powder lot to another.</p><p></p><p>You get a new jug of powder, your pet load no longer drives tacks?</p><p>wonder why? It has to be tweaked.</p><p></p><p>Extruded powders and those labelled extreme or insensitive act best, but even they can whacky out on the ends of the temp curve vs. burn rate and pressure.</p><p></p><p>Temp. insensitivity in cold weather does not guarantee temp. insensitivity in hot weather either.</p><p>That is my main point.</p></blockquote><p></p>
[QUOTE="Veteran, post: 2317072, member: 118038"] Here's the thing ......I don't generally like the freeze test though in this specific case it may be informative where going from hotter to cooler or cold climate and you are most worried about loss in velocity. The issue I have w freeze test is when one develops a hot max velocity pressure load in moderate weather and then tries to use it in very hot weather. I think that freeze test is then useless in that case. Because when a load is a hairs breadth from 65,000 psi at 70 degrees and you take it to 100 degrees, and you think your powder is "insensitive" cause you did a freeze test, I hope you have unlimited surgical insurance and a reputable life insurer.......because IMHO losing speed and pressure in cold weather aint the same fps gain in the hot direction. The closer your load is to "rifle scrap metal" at 70 degrees, it becomes a bomb at 100. The response curve for burn rate vs. temp may be somewhat linear over reasonable temp. ranges at reasonable charge weights. But once you get out on the limb, that curve becomes exponential on the margin, and it will either surprise you or hurt you. Just my opinion. Ie, hot loads taken into hot weather will act bizarro world. Hot loads taken into cold weather Arent a safety issue, but more of a hunting accuracy and performance issue. Like Clint Eastwood says, a man has gotta know his powder's limitations......🙂🤔 Burn rates are not a constant! They are not even very consistent from one powder lot to another. You get a new jug of powder, your pet load no longer drives tacks? wonder why? It has to be tweaked. Extruded powders and those labelled extreme or insensitive act best, but even they can whacky out on the ends of the temp curve vs. burn rate and pressure. Temp. insensitivity in cold weather does not guarantee temp. insensitivity in hot weather either. That is my main point. [/QUOTE]
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