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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Headspace -vs- Case Stretch
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<blockquote data-quote="woods" data-source="post: 668768" data-attributes="member: 6042"><p>+2</p><p></p><p>The combination of the firing pin strike and the jetting action of the firing primer against the inside of the primer pocket will push the case as far forward in the chamber as possible and the case will stretch rearward to the bolt face. If you are shooting an unbelted case the case shoulder and chamber shoulder is the contact point and there is not much stretching since the gap between the case shoulder and chamber shoulder on new brass is in the range of .001" to .011" (largest I've measured). But on a belted case the belt will stop the case from moving forward in the chamber and that gap will be from .015" to .040"</p><p></p><p><img src="http://img.photobucket.com/albums/v663/bwestfall/RELOADING/DSCN1696.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p><img src="http://img.photobucket.com/albums/v663/bwestfall/RELOADING/DSCN1697.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>with most being around .020"</p><p></p><p>Still belted cases will stretch at the pressure ring just above the solid case head. The excessive stretching on belted cases is why they are more prone to a case head separation. The initial stretch is much greater than on an unbelted case. Also why it is important to headspace a belted case on the shoulder as soon as possible.</p><p></p><p>IMO the neck swells first then the case body and then stretched back to the bolt face. The neck needs to seal the chamber otherwise there would be a lot of escaping gas around it that would discolor and cave in the thin neck brass.</p></blockquote><p></p>
[QUOTE="woods, post: 668768, member: 6042"] +2 The combination of the firing pin strike and the jetting action of the firing primer against the inside of the primer pocket will push the case as far forward in the chamber as possible and the case will stretch rearward to the bolt face. If you are shooting an unbelted case the case shoulder and chamber shoulder is the contact point and there is not much stretching since the gap between the case shoulder and chamber shoulder on new brass is in the range of .001" to .011" (largest I've measured). But on a belted case the belt will stop the case from moving forward in the chamber and that gap will be from .015" to .040" [IMG]http://img.photobucket.com/albums/v663/bwestfall/RELOADING/DSCN1696.jpg[/IMG] [IMG]http://img.photobucket.com/albums/v663/bwestfall/RELOADING/DSCN1697.jpg[/IMG] with most being around .020" Still belted cases will stretch at the pressure ring just above the solid case head. The excessive stretching on belted cases is why they are more prone to a case head separation. The initial stretch is much greater than on an unbelted case. Also why it is important to headspace a belted case on the shoulder as soon as possible. IMO the neck swells first then the case body and then stretched back to the bolt face. The neck needs to seal the chamber otherwise there would be a lot of escaping gas around it that would discolor and cave in the thin neck brass. [/QUOTE]
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Headspace -vs- Case Stretch
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