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Rifles, Reloading, Optics, Equipment
Reloading
New to mandrel expanders have questions
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<blockquote data-quote="Mikecr" data-source="post: 1842060" data-attributes="member: 1521"><p>Be careful with assumptions about a collet approach.</p><p>The object here is to get bullets pointed straight.</p><p>Outside action only will leave thickness variance in necks in interference with straight seating. </p><p>The purpose of expanding mandrel use is not to set tension, but to drive that variance outward -away from seating bullets, for straighter overall ammo.</p><p></p><p>A basic thing also that every reloader needs to understand is that neck tension is not whatever interference you set.</p><p>Neck tension is spring back gripping of bullets. And necks spring back less than 1thou, so any interference beyond this is not contributing to tension, as bullet seating is merely expanding/undoing that excess.</p><p></p><p>Either downsizing(with a bushing) or upsizing (with a mandrel), or in fact any sizing, means brass is taken to yield, and does not fully spring back to pre-sizing dimension.</p><p>Sizing adds energy to brass, and that brass will try to get back to lowest energy level. Much of this happens with initial spring back, but that spring back also continues over time (if it can).</p><p>If you last sizing action with necks is down sizing, those necks will spring back outward initially, and they will continue to spring back outward over time. This, reducing neck tension over time.</p><p>Neck expansion in general should be done to ensure that there will always be sufficient tension.</p><p>This expansion is best done with a mandrel rather than bullets (which are terrible expanders). </p><p>I call mandrel expansion 'pre-seating'.</p><p></p><p>If your mandrel is 1thou under cal, this is what you can successfully do:</p><p>Set your bushing ~3thou under loaded neck OD. After downsizing with this, the neck will spring back outward a bit under 1thou to maybe ~2.25thou under cal. Then the expander mandrel will size up from here and the neck will spring back inward a bit under 1thou from that to ~1.25thou under cal. That in itself is excess but not by much. It'll work just fine.</p><p>These numbers are variables subject to trial & error because the bushing results vary with sizing amount (angular variances).</p><p></p><p>Last thing: NEVER FL size necks.</p><p>Another tread to explain that, but just don't...</p></blockquote><p></p>
[QUOTE="Mikecr, post: 1842060, member: 1521"] Be careful with assumptions about a collet approach. The object here is to get bullets pointed straight. Outside action only will leave thickness variance in necks in interference with straight seating. The purpose of expanding mandrel use is not to set tension, but to drive that variance outward -away from seating bullets, for straighter overall ammo. A basic thing also that every reloader needs to understand is that neck tension is not whatever interference you set. Neck tension is spring back gripping of bullets. And necks spring back less than 1thou, so any interference beyond this is not contributing to tension, as bullet seating is merely expanding/undoing that excess. Either downsizing(with a bushing) or upsizing (with a mandrel), or in fact any sizing, means brass is taken to yield, and does not fully spring back to pre-sizing dimension. Sizing adds energy to brass, and that brass will try to get back to lowest energy level. Much of this happens with initial spring back, but that spring back also continues over time (if it can). If you last sizing action with necks is down sizing, those necks will spring back outward initially, and they will continue to spring back outward over time. This, reducing neck tension over time. Neck expansion in general should be done to ensure that there will always be sufficient tension. This expansion is best done with a mandrel rather than bullets (which are terrible expanders). I call mandrel expansion 'pre-seating'. If your mandrel is 1thou under cal, this is what you can successfully do: Set your bushing ~3thou under loaded neck OD. After downsizing with this, the neck will spring back outward a bit under 1thou to maybe ~2.25thou under cal. Then the expander mandrel will size up from here and the neck will spring back inward a bit under 1thou from that to ~1.25thou under cal. That in itself is excess but not by much. It'll work just fine. These numbers are variables subject to trial & error because the bushing results vary with sizing amount (angular variances). Last thing: NEVER FL size necks. Another tread to explain that, but just don't... [/QUOTE]
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New to mandrel expanders have questions
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