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Rifles, Reloading, Optics, Equipment
Reloading
Virgin brass vs. fire formed
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<blockquote data-quote="woods" data-source="post: 317000" data-attributes="member: 6042"><p>Hey John</p><p></p><p>In the example where he said the firing pin pushes the case forward to the shoulder, that would not apply with a belted case. I have measured the amount of case travel in a few belted case chambers (headspace) and it varied from .000" to .007" because the belt stops forward movement. Now there is still significant space between the case shoulder and the chamber shoulder in the belted mags which is called "head clearance" and that can be as much as .030". But with the case forward movement stopped, it is not true that the firing pin pushes the case forward to contact. In a belted case the brass has to expand forward toward the shoulder.</p><p></p><p>In an unbelted case the firing pin and the explosion of the primer pushing on the inside of the primer hole propels the case forward to contact at the shoulder immediately and the case expands backward to the bolt face. There is usually significantly less headspace on an unbelted case than there is head clearance on a belted one. Someone mentioned .020" on a 30-06 case and that is more than it should be on an unbelted case. On my 30-06, the headspace generally ranges from .010" to .012" depending upon the brass.</p><p></p><p>Also, if your neck thicknesses vary from .0115" to .017" you have a problem. Even with outside neck turning you are not going to do a lot of good with those case. Reference this diagram that shows how neck turning will not correct a problem of too much neck thickness variation</p><p><img src="http://img.photobucket.com/albums/v663/bwestfall/CASE%20PREP/neckcenter.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>If I were you I would separate the cases based upon neck thickness variation. Those with little to no variation are worth your trouble to neck turn (.002" or less), but those with the large variations will continue to degrade your accuracy. </p><p></p><p>As far as new vs. fire formed, I get my best accuracy and consistancy with fire formed partial full length resized but only when I pay attention to consistant bullet release. That means cleaned, steel wooled, mica'ed and annealed when necessary.</p><p></p><p>JMHO</p></blockquote><p></p>
[QUOTE="woods, post: 317000, member: 6042"] Hey John In the example where he said the firing pin pushes the case forward to the shoulder, that would not apply with a belted case. I have measured the amount of case travel in a few belted case chambers (headspace) and it varied from .000" to .007" because the belt stops forward movement. Now there is still significant space between the case shoulder and the chamber shoulder in the belted mags which is called "head clearance" and that can be as much as .030". But with the case forward movement stopped, it is not true that the firing pin pushes the case forward to contact. In a belted case the brass has to expand forward toward the shoulder. In an unbelted case the firing pin and the explosion of the primer pushing on the inside of the primer hole propels the case forward to contact at the shoulder immediately and the case expands backward to the bolt face. There is usually significantly less headspace on an unbelted case than there is head clearance on a belted one. Someone mentioned .020" on a 30-06 case and that is more than it should be on an unbelted case. On my 30-06, the headspace generally ranges from .010" to .012" depending upon the brass. Also, if your neck thicknesses vary from .0115" to .017" you have a problem. Even with outside neck turning you are not going to do a lot of good with those case. Reference this diagram that shows how neck turning will not correct a problem of too much neck thickness variation [IMG]http://img.photobucket.com/albums/v663/bwestfall/CASE%20PREP/neckcenter.jpg[/IMG] If I were you I would separate the cases based upon neck thickness variation. Those with little to no variation are worth your trouble to neck turn (.002" or less), but those with the large variations will continue to degrade your accuracy. As far as new vs. fire formed, I get my best accuracy and consistancy with fire formed partial full length resized but only when I pay attention to consistant bullet release. That means cleaned, steel wooled, mica'ed and annealed when necessary. JMHO [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Virgin brass vs. fire formed
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