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Rifles, Reloading, Optics, Equipment
Reloading
Traditional Press Seating Die vs. In Line Arbor Press
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<blockquote data-quote="Mikecr" data-source="post: 2960633" data-attributes="member: 1521"><p>This is true. </p><p>The root cause of our runout is <strong>sizing of thickness variance</strong>.</p><p>So the 1st step in making straight ammo is to measure brass thickness variance, and cull away offending cases.</p><p>2nd step is to reduce sizing of what remains. </p><p>For necks, don't excessively size, and never size donut area (FL sizing of necks).</p><p>For the same reason, avoid sizing of web areas.</p><p></p><p>Tension is a different matter that is not adjusted with downsizing beyond normal spring back (excess interference).</p><p>Neck tension is hoop spring back <strong>gripping force against an area of bullet bearing</strong>. It would properly be expressed in PSI.</p><p>Since the spring back force of brass is limited per given parameters, adjustment of tension is through area applied. </p><p>The <u>area</u> is seated bearing available for a sizing <u>length</u> to grip.</p><p>This is what I adjust with neck bushings, and I can watch it across a chronograph.</p><p>An exception to this is with neck sizing length beyond seated bullet bearing. That sets up bearing-base binding, and brings donut brass and shoulder angles into neck tension. While it presents higher tension, there is way more tension variance in it.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 2960633, member: 1521"] This is true. The root cause of our runout is [B]sizing of thickness variance[/B]. So the 1st step in making straight ammo is to measure brass thickness variance, and cull away offending cases. 2nd step is to reduce sizing of what remains. For necks, don't excessively size, and never size donut area (FL sizing of necks). For the same reason, avoid sizing of web areas. Tension is a different matter that is not adjusted with downsizing beyond normal spring back (excess interference). Neck tension is hoop spring back [B]gripping force against an area of bullet bearing[/B]. It would properly be expressed in PSI. Since the spring back force of brass is limited per given parameters, adjustment of tension is through area applied. The [U]area[/U] is seated bearing available for a sizing [U]length[/U] to grip. This is what I adjust with neck bushings, and I can watch it across a chronograph. An exception to this is with neck sizing length beyond seated bullet bearing. That sets up bearing-base binding, and brings donut brass and shoulder angles into neck tension. While it presents higher tension, there is way more tension variance in it. [/QUOTE]
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Traditional Press Seating Die vs. In Line Arbor Press
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