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Rifles, Reloading, Optics, Equipment
Reloading
Neck Sizing
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<blockquote data-quote="boomtube" data-source="post: 828536" data-attributes="member: 9215"><p>AZShooter: "<em>Continue to lower FL die till it sizes the brass enough for either a fit with slight bolt closing resistance or one that allows you to close the bolt without resistance but no more. There is a fine line between the two settings. Once you find that spot you can repeat it by using feeler gauges to measure the gap between the shell holder and end of die body</em>."</p><p> </p><p>We can duplicate the die set up that way but we can't precisely repeat the shoulder sizing that way. Case spring back varies by brand and production lot, ditto the normal work hardening as it's recycled. I gave up any rote method of die adjustment decades ago and adjust my sizers to match my chambers each time I load a batch.</p><p> </p><p>What never gets mentioned in how tight we adjust a FL sizer for chamber fit is that it hardly matters to a fine degree anyway. The firing pin impact drives each case fully forward in the chamber and then the primer discharge drives it a tad deeper so rimless case shoulders are always going to be fully forward and centered in the chamber. Pressure will expand the thin necks and fore part (probably before the bullet moves more than a small amount) and lock the case in that full forward position as pressure increases to stretch the base back into contact with the bolt face. Thus "proper" - minimum - FL resizing helps limit case stretch more than it affects acuracy. Making accurate ammo involves much more than neck sizing, "partial" FL sizing or highly precise sized shoulder placement.</p><p> </p><p>Normal neck sizing below the neck's contact with the seated bullet is meaningless.</p></blockquote><p></p>
[QUOTE="boomtube, post: 828536, member: 9215"] AZShooter: "[I]Continue to lower FL die till it sizes the brass enough for either a fit with slight bolt closing resistance or one that allows you to close the bolt without resistance but no more. There is a fine line between the two settings. Once you find that spot you can repeat it by using feeler gauges to measure the gap between the shell holder and end of die body[/I]." We can duplicate the die set up that way but we can't precisely repeat the shoulder sizing that way. Case spring back varies by brand and production lot, ditto the normal work hardening as it's recycled. I gave up any rote method of die adjustment decades ago and adjust my sizers to match my chambers each time I load a batch. What never gets mentioned in how tight we adjust a FL sizer for chamber fit is that it hardly matters to a fine degree anyway. The firing pin impact drives each case fully forward in the chamber and then the primer discharge drives it a tad deeper so rimless case shoulders are always going to be fully forward and centered in the chamber. Pressure will expand the thin necks and fore part (probably before the bullet moves more than a small amount) and lock the case in that full forward position as pressure increases to stretch the base back into contact with the bolt face. Thus "proper" - minimum - FL resizing helps limit case stretch more than it affects acuracy. Making accurate ammo involves much more than neck sizing, "partial" FL sizing or highly precise sized shoulder placement. Normal neck sizing below the neck's contact with the seated bullet is meaningless. [/QUOTE]
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