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Rifles, Reloading, Optics, Equipment
Reloading
Full length sizing VS neck sizing
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<blockquote data-quote="QuietTexan" data-source="post: 2566047" data-attributes="member: 116181"><p>What you're missing is <strong>total movement</strong> of the brass, inwards and outwards.</p><p></p><p>Start with a regular FL die. Say the brass moves inwards 0.005" when sized down because the neck dimension inside the die is very small to ensure it sizes every case that goes in to the die is sized, then the expander pulls back through and moves it 0.003" out. Resulting neck ID is -0.002" under caliber. Total movement - 0.008".</p><p></p><p>Now switch to a bushing-body die. You pick the correct bushing and the neck moves in 0.002" and then the expander only pulls it back out 0.001". Resulting neck ID is -0.002" under caliber. Total movement - 0.003"</p><p></p><p>Next refinement, you use mandrels instead of the expander ball. Mandrels come in half-thou (0.0005") increments. Bushing sizes down 0.002", mandrel upsizes 0.0005". Resulting neck ID is -0.0015" under caliber. Total movement - 0.0025".</p><p></p><p>You can go to a -0.001" bushing and get the neck ID to -0.0005" and total movement of 0.0015". But in my world that's a little light in terms of holding the bullet. Realistically no way to move less in and out anymore. </p><p></p><p>Enter length of neck sizing. Neck of our hypothetical case is 0.260" long. An FL die will size all 0.260" of it, because the die is a single cut of metal so there are no gaps where brass isn't resized. Bushing die will size 0.210" of it, because a bushing die generally always leaves a small unsized portion of the neck. Then you back the bushing out (say with the mic on a Redding Type S Comp Neck Sizing die) and you can size all 0.210", or half at 0.130", or two-thirds at 0.174". Total movement still 0.0025" in and out, but less of the beck is moving. Less length of neck sized = neck has less grip overall on the bullet, but the part that's holding can hold tighter than if you set the entire length of the neck at a lighter setting.</p><p></p><p>Total movement of the neck is what results in work hardening. Total movement can also result in permanently yielding the case neck to where it acts differently than it did before.</p><p></p><p>Chamber diameter comes in to play here also, how much the neck is expanding when fired and what diameter it returns to, then is sized down to, then is expanded to by a mandrel, then ultimately by the bullet.</p></blockquote><p></p>
[QUOTE="QuietTexan, post: 2566047, member: 116181"] What you're missing is [B]total movement[/B] of the brass, inwards and outwards. Start with a regular FL die. Say the brass moves inwards 0.005" when sized down because the neck dimension inside the die is very small to ensure it sizes every case that goes in to the die is sized, then the expander pulls back through and moves it 0.003" out. Resulting neck ID is -0.002" under caliber. Total movement - 0.008". Now switch to a bushing-body die. You pick the correct bushing and the neck moves in 0.002" and then the expander only pulls it back out 0.001". Resulting neck ID is -0.002" under caliber. Total movement - 0.003" Next refinement, you use mandrels instead of the expander ball. Mandrels come in half-thou (0.0005") increments. Bushing sizes down 0.002", mandrel upsizes 0.0005". Resulting neck ID is -0.0015" under caliber. Total movement - 0.0025". You can go to a -0.001" bushing and get the neck ID to -0.0005" and total movement of 0.0015". But in my world that's a little light in terms of holding the bullet. Realistically no way to move less in and out anymore. Enter length of neck sizing. Neck of our hypothetical case is 0.260" long. An FL die will size all 0.260" of it, because the die is a single cut of metal so there are no gaps where brass isn't resized. Bushing die will size 0.210" of it, because a bushing die generally always leaves a small unsized portion of the neck. Then you back the bushing out (say with the mic on a Redding Type S Comp Neck Sizing die) and you can size all 0.210", or half at 0.130", or two-thirds at 0.174". Total movement still 0.0025" in and out, but less of the beck is moving. Less length of neck sized = neck has less grip overall on the bullet, but the part that's holding can hold tighter than if you set the entire length of the neck at a lighter setting. Total movement of the neck is what results in work hardening. Total movement can also result in permanently yielding the case neck to where it acts differently than it did before. Chamber diameter comes in to play here also, how much the neck is expanding when fired and what diameter it returns to, then is sized down to, then is expanded to by a mandrel, then ultimately by the bullet. [/QUOTE]
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Full length sizing VS neck sizing
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