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Rifles, Reloading, Optics, Equipment
Reloading
Mechanics of a crush fit
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<blockquote data-quote="woods" data-source="post: 943990" data-attributes="member: 6042"><p>I often run across those who say that a case can not grow larger than the chamber, i.e. "how could it?"</p><p></p><p>So I have a theory, and that's all it can be since what happens in the chamber is hidden from us. Sorta like astronomers inferring the existence of a black hole by other factors.</p><p></p><p>So, 2 things make a crush fit possible:</p><p></p><p>1. The ignition of the primer inside the primer pocket propels the case forward with force. In my tests and on other websites, an empty case fired with a live primer will have the headspace reduced by as much as .002"</p><p></p><p>2. In a load firing, the shoulder gets pushed back by the primer explosion, the case walls expand to the chamber walls, the case head gets pushed back to the bolt face (case shoulder still hard against the chamber shoulder) and the case walls springback (allowing extraction). Upon ejection the pent up springback forces of the shoulder move it forward (it was pushed back now springback is forward)</p><p></p><p>Perhaps this is common knowledge but I've never seen it explained so I'm looking for validation, rejection or discussion</p><p></p><p>Thanks</p></blockquote><p></p>
[QUOTE="woods, post: 943990, member: 6042"] I often run across those who say that a case can not grow larger than the chamber, i.e. "how could it?" So I have a theory, and that's all it can be since what happens in the chamber is hidden from us. Sorta like astronomers inferring the existence of a black hole by other factors. So, 2 things make a crush fit possible: 1. The ignition of the primer inside the primer pocket propels the case forward with force. In my tests and on other websites, an empty case fired with a live primer will have the headspace reduced by as much as .002" 2. In a load firing, the shoulder gets pushed back by the primer explosion, the case walls expand to the chamber walls, the case head gets pushed back to the bolt face (case shoulder still hard against the chamber shoulder) and the case walls springback (allowing extraction). Upon ejection the pent up springback forces of the shoulder move it forward (it was pushed back now springback is forward) Perhaps this is common knowledge but I've never seen it explained so I'm looking for validation, rejection or discussion Thanks [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Mechanics of a crush fit
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