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Rifles, Reloading, Optics, Equipment
Reloading
Sorting Brass by weight
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<blockquote data-quote="Mikecr" data-source="post: 605529" data-attributes="member: 1521"><p>And my counter;</p><p></p><p>All powders vary in burn rate due to ever changing load density, confinement, and pressure at any given moment within a barrel.</p><p></p><p>Powder burn is very sensitive to initial confinement. </p><p>Put a 1/3 charge of powder in an open case, load carefully(barrel upward), and on firing you get WUMP...</p><p>Now do the same with a fold of toilet paper set on the powder, and you get BOOM.</p><p>This is the functioning of cream of wheat fireforming, and brass weight is not a factor in it.</p><p>The confinement offered by that paper, tiny as you can imagine, is significant. </p><p>The flame front literally bounces off it to light a higher percentage of powder granule surface at a resultant higher rate.</p><p></p><p>Another confinement test, caused by load density and/or proximity; with loaded cartridges that hold a relatively low load density(case filled to body-shoulder), you can measure a considerable velocity shift, again with no change in brass weight.</p><p>Just hand load one with the barrel pointed straight up, carefully lower the gun onto a rest so that the powder stays rearward in the case. </p><p>Fire it across a chronograph and note POI.</p><p>Then load case with the barrel pointed straight down, carefully raise the gun to a rest so that the powder stays forward in the case.</p><p>Fire it across a chronograph and note POI.</p><p>You will see velocity higher when powder was lit most rearward in the case.</p><p>This is one reason load density is important -beyond getting enough into a case. Load density is really confinement -caused by the powder itself.</p><p></p><p>Pressure itself affects every powder burn rate, all along the way, from primer ignition to muzzle release.</p><p>When you jam a bullet into the lands, you not only increase in pressure before full land engravement, but you speed powder burn RATE to a different position on a burn rate chart. Advantage in this depends on consistency of it, as it changes MV and barrel timing. </p><p>This again, can be independent of brass weight.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 605529, member: 1521"] And my counter; All powders vary in burn rate due to ever changing load density, confinement, and pressure at any given moment within a barrel. Powder burn is very sensitive to initial confinement. Put a 1/3 charge of powder in an open case, load carefully(barrel upward), and on firing you get WUMP... Now do the same with a fold of toilet paper set on the powder, and you get BOOM. This is the functioning of cream of wheat fireforming, and brass weight is not a factor in it. The confinement offered by that paper, tiny as you can imagine, is significant. The flame front literally bounces off it to light a higher percentage of powder granule surface at a resultant higher rate. Another confinement test, caused by load density and/or proximity; with loaded cartridges that hold a relatively low load density(case filled to body-shoulder), you can measure a considerable velocity shift, again with no change in brass weight. Just hand load one with the barrel pointed straight up, carefully lower the gun onto a rest so that the powder stays rearward in the case. Fire it across a chronograph and note POI. Then load case with the barrel pointed straight down, carefully raise the gun to a rest so that the powder stays forward in the case. Fire it across a chronograph and note POI. You will see velocity higher when powder was lit most rearward in the case. This is one reason load density is important -beyond getting enough into a case. Load density is really confinement -caused by the powder itself. Pressure itself affects every powder burn rate, all along the way, from primer ignition to muzzle release. When you jam a bullet into the lands, you not only increase in pressure before full land engravement, but you speed powder burn RATE to a different position on a burn rate chart. Advantage in this depends on consistency of it, as it changes MV and barrel timing. This again, can be independent of brass weight. [/QUOTE]
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