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Rifles, Reloading, Optics, Equipment
Reloading
Why such varying headspace measurement on fired cases
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<blockquote data-quote="bigedp51" data-source="post: 1517919" data-attributes="member: 28965"><p>Many times you have to fire a case several times before the case becomes a snug fit and shoulder needs to be bumped back. This varies with chamber pressure and brass spring back after firing.</p><p></p><p>Take one of your 1.630 length cases with the primer removed and and measure from the base to the case mouth and write it down.</p><p></p><p>Now just using your fingers start a fired spent primer into the primer pocket.</p><p></p><p><img src="https://i.imgur.com/SgwqgaU.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><img src="https://i.imgur.com/oNIvIiX.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p><img src="https://i.imgur.com/zQxlYGp.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Now chamber the case, close the bolt and let the bolt face seat the primer.</p><p></p><p>Now measure the case again from the base of the primer to the case mouth.</p><p></p><p>Now subtract the first case measurement from the second and this is the primer protrusion.</p><p></p><p>The amount of primer protrusion is also your head clearance or the air space between the case and the bolt face. Normally on a bolt action you want .001 to .002 shoulder bump that should also be your head clearance.</p><p></p><p><img src="https://i.imgur.com/HK76WCp.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>The primer protrusion will tell you how much shorter the case is than the chamber at the shoulder. This will give you a idea of actual chamber headspace. </p><p></p><p></p><p>When you full length resize you squeeze the case and it will become longer. And if the die is adjusted to high off the shell holder you can actually make the case headspace longer than the chamber.</p><p></p><p><img src="https://i.imgur.com/wm05ArY.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Place a .010 feeler gauge on top of the shell holder and screw your die down until the die contacts the feeler gauge.</p><p></p><p><img src="https://i.imgur.com/7FfXhJ7.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Now resize a case and try chambering the case and see if you can close the bolt. If it does not chamber then use a .008, .006, .004 etc feeler gauge until the case chambers without resistance.</p></blockquote><p></p>
[QUOTE="bigedp51, post: 1517919, member: 28965"] Many times you have to fire a case several times before the case becomes a snug fit and shoulder needs to be bumped back. This varies with chamber pressure and brass spring back after firing. Take one of your 1.630 length cases with the primer removed and and measure from the base to the case mouth and write it down. Now just using your fingers start a fired spent primer into the primer pocket. [IMG]https://i.imgur.com/SgwqgaU.jpg[/IMG] [IMG]https://i.imgur.com/oNIvIiX.jpg[/IMG] [IMG]https://i.imgur.com/zQxlYGp.jpg[/IMG] Now chamber the case, close the bolt and let the bolt face seat the primer. Now measure the case again from the base of the primer to the case mouth. Now subtract the first case measurement from the second and this is the primer protrusion. The amount of primer protrusion is also your head clearance or the air space between the case and the bolt face. Normally on a bolt action you want .001 to .002 shoulder bump that should also be your head clearance. [IMG]https://i.imgur.com/HK76WCp.jpg[/IMG] The primer protrusion will tell you how much shorter the case is than the chamber at the shoulder. This will give you a idea of actual chamber headspace. When you full length resize you squeeze the case and it will become longer. And if the die is adjusted to high off the shell holder you can actually make the case headspace longer than the chamber. [img]https://i.imgur.com/wm05ArY.gif[/img] Place a .010 feeler gauge on top of the shell holder and screw your die down until the die contacts the feeler gauge. [img]https://i.imgur.com/7FfXhJ7.jpg[/img] Now resize a case and try chambering the case and see if you can close the bolt. If it does not chamber then use a .008, .006, .004 etc feeler gauge until the case chambers without resistance. [/QUOTE]
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Why such varying headspace measurement on fired cases
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