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Rifles, Reloading, Optics, Equipment
Reloading
Neck sizing question
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<blockquote data-quote="Mikecr" data-source="post: 1225388" data-attributes="member: 1521"><p>Just .001 of interference fit is as much bullet grip (tension) as springback will provide.</p><p>The recommended -002 under loaded diameter accounts for ~.001 springing back outward with die release, leaving ~.001 interference fit. When you seat the bullet bearing, it will expand the neck outward another .001, which is all the spring back provided by brass, and minimal sizing beyond it.</p><p></p><p>The missing part of this instruction is pre-expansion of necks, which should always be done prior to bullet seating. If you're bushing is actually leaving necks further than .001 under cal, which is likely and depending on neck size produced by your chamber, then necks should be expanded with a hardened mandrel/button instead of expanding with soft bullet jackets. This also drives thickness variance and/or donut area outward, away from seating bullet bearing (reducing loaded runout).</p><p></p><p>Neck tension is adjusted in sizing by LENGTH of that sizing, given .001 under cal interference fit. Any more than .001 under against seated bearing is excess and does nothing for you.</p><p>Beyond seated bearing, greater interference does increase tension (dramatically) and with it, causing greater tension variance.</p><p>By far, most reloaders should never FL size necks.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 1225388, member: 1521"] Just .001 of interference fit is as much bullet grip (tension) as springback will provide. The recommended -002 under loaded diameter accounts for ~.001 springing back outward with die release, leaving ~.001 interference fit. When you seat the bullet bearing, it will expand the neck outward another .001, which is all the spring back provided by brass, and minimal sizing beyond it. The missing part of this instruction is pre-expansion of necks, which should always be done prior to bullet seating. If you're bushing is actually leaving necks further than .001 under cal, which is likely and depending on neck size produced by your chamber, then necks should be expanded with a hardened mandrel/button instead of expanding with soft bullet jackets. This also drives thickness variance and/or donut area outward, away from seating bullet bearing (reducing loaded runout). Neck tension is adjusted in sizing by LENGTH of that sizing, given .001 under cal interference fit. Any more than .001 under against seated bearing is excess and does nothing for you. Beyond seated bearing, greater interference does increase tension (dramatically) and with it, causing greater tension variance. By far, most reloaders should never FL size necks. [/QUOTE]
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Reloading
Neck sizing question
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