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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
How to blowup your rifle
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<blockquote data-quote="Pdvdh" data-source="post: 1386024" data-attributes="member: 4191"><p>The elastic yield strain for brass cases is low enough that most of us exceed it while working up to maximum pressure loads.</p><p>The elastic yield limit for the steel and brass is exceeded whenever the steel or brass has permanently deformed under tensile force.</p><p>I measure case expansion just forward of my cartridge rims while developing loads. When I measure 0.0005" or more expansion after firing a new casing, I accept that as a maximum load. The permanent expansion also means the case pressure developed tension/strain in the case head which exceeded the elastic yield strain of the brass case head.</p><p>In other words, the elastic strain limit for the brass casing provides little value in determining a minimum case pressure that could excite any of us. We commonly exceed it during load work up. Primer pocket expansion? Again it means the elastic yield limit of the case has been exceeded.</p><p>Whether or not permanent deformation occurs is based on two factors: 1) the modulus of elasticity of the metal and 2) the thickness or cross sectional area of the metal material.</p><p>If there's an engineer that's more up on their mechanics of materials education/knowledge than I, feel free to refine this explanation closer to dead nutz on. I believe the above to be correct, or I wouldn't have just posted it.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 1386024, member: 4191"] The elastic yield strain for brass cases is low enough that most of us exceed it while working up to maximum pressure loads. The elastic yield limit for the steel and brass is exceeded whenever the steel or brass has permanently deformed under tensile force. I measure case expansion just forward of my cartridge rims while developing loads. When I measure 0.0005" or more expansion after firing a new casing, I accept that as a maximum load. The permanent expansion also means the case pressure developed tension/strain in the case head which exceeded the elastic yield strain of the brass case head. In other words, the elastic strain limit for the brass casing provides little value in determining a minimum case pressure that could excite any of us. We commonly exceed it during load work up. Primer pocket expansion? Again it means the elastic yield limit of the case has been exceeded. Whether or not permanent deformation occurs is based on two factors: 1) the modulus of elasticity of the metal and 2) the thickness or cross sectional area of the metal material. If there's an engineer that's more up on their mechanics of materials education/knowledge than I, feel free to refine this explanation closer to dead nutz on. I believe the above to be correct, or I wouldn't have just posted it. [/QUOTE]
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