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Rifles, Reloading, Optics, Equipment
Reloading
The importance of case trim
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<blockquote data-quote="sab" data-source="post: 1645790" data-attributes="member: 1548"><p>eschafer and Edd:</p><p></p><p>Brass is an elastic material, as is the steel making up the chamber, but only to a certain point. After that, they become plastic (permanently expand). When pressures are too high, the high pressures inside the case will expand the case and the chamber beyond their sizes with just atmospheric pressure in the chamber. Because the brass transitions from elastic deformation (able to "spring back") to plastic deformation (permanently stretched) at a lower pressure, as the pressure subsides, the chamber springs back to it's original, smaller diameter, but the case only springs back so far, leaving it larger after firing. This phenomenon is what causes a stuck case. Together, the case and chamber expanded under pressure, and when the pressure dropped, the case was left larger than the chamber, but the chamber is much stronger, so it compressed the case elastically, causing the case to be stuck in the chamber. Once removed, the case springs back to the diameter that is larger than the chamber.</p><p></p><p>I hope this makes sense. It's a complicated situation, and I remember sitting in my materials science class 30+ years ago and thinking about a rifle firing when the professor was explaining a stress-strain curve to us. Today, a student having those thoughts best not share them, or they'll be suspended for even thinking about guns...</p><p></p><p>SAB</p></blockquote><p></p>
[QUOTE="sab, post: 1645790, member: 1548"] eschafer and Edd: Brass is an elastic material, as is the steel making up the chamber, but only to a certain point. After that, they become plastic (permanently expand). When pressures are too high, the high pressures inside the case will expand the case and the chamber beyond their sizes with just atmospheric pressure in the chamber. Because the brass transitions from elastic deformation (able to "spring back") to plastic deformation (permanently stretched) at a lower pressure, as the pressure subsides, the chamber springs back to it's original, smaller diameter, but the case only springs back so far, leaving it larger after firing. This phenomenon is what causes a stuck case. Together, the case and chamber expanded under pressure, and when the pressure dropped, the case was left larger than the chamber, but the chamber is much stronger, so it compressed the case elastically, causing the case to be stuck in the chamber. Once removed, the case springs back to the diameter that is larger than the chamber. I hope this makes sense. It's a complicated situation, and I remember sitting in my materials science class 30+ years ago and thinking about a rifle firing when the professor was explaining a stress-strain curve to us. Today, a student having those thoughts best not share them, or they'll be suspended for even thinking about guns... SAB [/QUOTE]
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The importance of case trim
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