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Rifles, Reloading, Optics, Equipment
Reloading
Pressure relative to distance from lands.
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<blockquote data-quote="woods" data-source="post: 356200" data-attributes="member: 6042"><p>The chart above has the same charge weight each time. The brass does not put up much resistance to the pressure and the case expands readily. What lowers the pressure is that the bullet is moving and if it hits the lands on the run then that diminishes the pressure needed for the bullet to engrave into the lands. Sort of a running start.</p><p></p><p>Barnes has some info here about 1/2 way down the newsletter</p><p></p><p><a href="http://www.barnesbullets.com/resources/newsletters/september-2007-barnes-bullet-n/" target="_blank">September 2007 Barnes Bullet-n Barnes Bullets</a></p><p></p><p>and Hornady has some info down at the bottom of this page</p><p></p><p><a href="http://www.hornady.com/ballistics-resource/internal" target="_blank">Internal Ballistics - Hornady Manufacturing, Inc</a></p><p></p><p>I have noticed the effect of seating away from the lands when loading for some 300 win mag and other calibers like 300 Wtby, 300RUM and 338RUM. If a rifle has a long throat or a short mag then it takes more powder to get velocity. The 300 win mag is a particularly good example as the distance to the lands from the case head to the lands can be the same in 2 guns but if one has a short mag then it will be slower than the one where you can load closer. Same combustion chamber size but different distance to the lands.</p><p></p><p>"Even with the same powder charge weight? Seating deeper wouldn't affect pressure?"</p><p></p><p>It will lower the pressure.</p></blockquote><p></p>
[QUOTE="woods, post: 356200, member: 6042"] The chart above has the same charge weight each time. The brass does not put up much resistance to the pressure and the case expands readily. What lowers the pressure is that the bullet is moving and if it hits the lands on the run then that diminishes the pressure needed for the bullet to engrave into the lands. Sort of a running start. Barnes has some info here about 1/2 way down the newsletter [url=http://www.barnesbullets.com/resources/newsletters/september-2007-barnes-bullet-n/]September 2007 Barnes Bullet-n Barnes Bullets[/url] and Hornady has some info down at the bottom of this page [url=http://www.hornady.com/ballistics-resource/internal]Internal Ballistics - Hornady Manufacturing, Inc[/url] I have noticed the effect of seating away from the lands when loading for some 300 win mag and other calibers like 300 Wtby, 300RUM and 338RUM. If a rifle has a long throat or a short mag then it takes more powder to get velocity. The 300 win mag is a particularly good example as the distance to the lands from the case head to the lands can be the same in 2 guns but if one has a short mag then it will be slower than the one where you can load closer. Same combustion chamber size but different distance to the lands. "Even with the same powder charge weight? Seating deeper wouldn't affect pressure?" It will lower the pressure. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Pressure relative to distance from lands.
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