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Rifles, Reloading, Optics, Equipment
Reloading
Chambered Round Alignment to Bore; Neck Sized vs Full Length Sized
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<blockquote data-quote="boomtube" data-source="post: 645774" data-attributes="member: 9215"><p><em>"Note that pin's got between 20 and 30 pounds of force that's gonna hit the chambered round's primer." </em></p><p> </p><p>And that force immediatly jams the cartridge fully forward into the chamber so hard it typically sets the shoulder back 1-2 thou. The simulteanous explosion of the primer through the restriction of the flash hole blows the primer cup firmly back against the bolt face; at that point, and no matter how the case was sized, the case is firmly held between the bolt and cone of the chamber shoulder. </p><p> </p><p>Bullets move fairly easily but inertia holds it momentarily as case pressure rapidly ramps up - it's been theorized that the neck and forward part of a case will have released the bullet and is firmly blown against the chamber before the bullet enters the rifling even if it was seated well off the lands. If so, the bullet initially 'hangs in space', certainly the base does, as it enters the bore proper, no matter how the case was sized. Thus, how any advantages due to FL vs. neck sized is open to question but it's clear there is no fixed 'best' way to do it.</p><p> </p><p>A big reason bullet runout happens is the inner and outter cylinders of necks are offten misaligned; if the neck is thin on the upper side of the mouth of a chambered round and thin at the bottom shoulder side then the bullet will be pointed 'up' no matter how the case is sized or if the ogive is pushed into the origin of the lands. That's why modest neck turning on cases to be fired in loose fitting factory chambers will reduce bullet runout and it MAY improve accuracy.</p></blockquote><p></p>
[QUOTE="boomtube, post: 645774, member: 9215"] [I]"Note that pin's got between 20 and 30 pounds of force that's gonna hit the chambered round's primer." [/I] And that force immediatly jams the cartridge fully forward into the chamber so hard it typically sets the shoulder back 1-2 thou. The simulteanous explosion of the primer through the restriction of the flash hole blows the primer cup firmly back against the bolt face; at that point, and no matter how the case was sized, the case is firmly held between the bolt and cone of the chamber shoulder. Bullets move fairly easily but inertia holds it momentarily as case pressure rapidly ramps up - it's been theorized that the neck and forward part of a case will have released the bullet and is firmly blown against the chamber before the bullet enters the rifling even if it was seated well off the lands. If so, the bullet initially 'hangs in space', certainly the base does, as it enters the bore proper, no matter how the case was sized. Thus, how any advantages due to FL vs. neck sized is open to question but it's clear there is no fixed 'best' way to do it. A big reason bullet runout happens is the inner and outter cylinders of necks are offten misaligned; if the neck is thin on the upper side of the mouth of a chambered round and thin at the bottom shoulder side then the bullet will be pointed 'up' no matter how the case is sized or if the ogive is pushed into the origin of the lands. That's why modest neck turning on cases to be fired in loose fitting factory chambers will reduce bullet runout and it MAY improve accuracy. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Chambered Round Alignment to Bore; Neck Sized vs Full Length Sized
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