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Rifles, Reloading, Optics, Equipment
Reloading
Redding competition shell holders - headspace
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<blockquote data-quote="bigedp51" data-source="post: 1520482" data-attributes="member: 28965"><p>Most GO and NO-GO gauges have .003 to .004 between the two gauges and used to set up new barrels.</p><p></p><p>"BUT" if you look at the SAAMI drawing below the case belt can vary from .212 to .220. And the chamber headspace minimum is .220 and maximum is .227. Meaning with a thin belt and a chamber at max headspace you have .015 head clearance or air space between the rear of the case and the bolt face.</p><p></p><p><img src="https://i.imgur.com/O3zQ5WP.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Rimmed and belted cases are from a earlier age when manufacturing tolerances were not up to the standards we have today. Below on the left a modern .450 Martini Henry cartridge and on the right a cartridge from 1879 Zulu war. And as you can see a rimmed or belted case could be made very crudely and still chamber and fire. </p><p></p><p><img src="https://i.imgur.com/sDrsB0Q.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Below a new unfired .303 British cases in a Wilson case gauge. And the rim is stopping the case from dropping further into the gauge and allowing the case to rest on its shoulder.</p><p></p><p><img src="https://i.imgur.com/RBeuevm.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Below a fired .303 British case in the Wilson gauge and resting on its case shoulder.</p><p></p><p><img src="https://i.imgur.com/HrqwFOG.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Below a new unfired .303 British case on the left, a once fired case in the middle, and on the right a case fired three times and full length resized each time. Meaning the case headspaced on its rim and not its shoulder and allowed to stretch excessively each firing. And a military Enfield rifle at max headspace of .074 and a case with a rim thickness of .058 will have .016 head clearance.</p><p></p><p><img src="https://i.imgur.com/NHlR9jO.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Bottom line, a belted cartridge with a rifle at max headspace of .227 and a case with a belt thickness of .212 will have .015 head clearance. And normally you want .001 to .002 shoulder bump after sizing that would be the same amount of head clearance when the cartridge is chambered. </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><img src="https://i.imgur.com/3cOMj9s.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p></blockquote><p></p>
[QUOTE="bigedp51, post: 1520482, member: 28965"] Most GO and NO-GO gauges have .003 to .004 between the two gauges and used to set up new barrels. "BUT" if you look at the SAAMI drawing below the case belt can vary from .212 to .220. And the chamber headspace minimum is .220 and maximum is .227. Meaning with a thin belt and a chamber at max headspace you have .015 head clearance or air space between the rear of the case and the bolt face. [IMG]https://i.imgur.com/O3zQ5WP.png[/IMG] Rimmed and belted cases are from a earlier age when manufacturing tolerances were not up to the standards we have today. Below on the left a modern .450 Martini Henry cartridge and on the right a cartridge from 1879 Zulu war. And as you can see a rimmed or belted case could be made very crudely and still chamber and fire. [img]https://i.imgur.com/sDrsB0Q.jpg[/img] Below a new unfired .303 British cases in a Wilson case gauge. And the rim is stopping the case from dropping further into the gauge and allowing the case to rest on its shoulder. [img]https://i.imgur.com/RBeuevm.jpg[/img] Below a fired .303 British case in the Wilson gauge and resting on its case shoulder. [img]https://i.imgur.com/HrqwFOG.jpg[/img] Below a new unfired .303 British case on the left, a once fired case in the middle, and on the right a case fired three times and full length resized each time. Meaning the case headspaced on its rim and not its shoulder and allowed to stretch excessively each firing. And a military Enfield rifle at max headspace of .074 and a case with a rim thickness of .058 will have .016 head clearance. [img]https://i.imgur.com/NHlR9jO.jpg[/img] Bottom line, a belted cartridge with a rifle at max headspace of .227 and a case with a belt thickness of .212 will have .015 head clearance. And normally you want .001 to .002 shoulder bump after sizing that would be the same amount of head clearance when the cartridge is chambered. [img]https://i.imgur.com/HK76WCp.jpg[/img] [img]https://i.imgur.com/3cOMj9s.jpg[/img] [/QUOTE]
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Redding competition shell holders - headspace
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