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Rifles, Reloading, Optics, Equipment
Reloading
Neck tension and max bullet grip force
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<blockquote data-quote="Mikecr" data-source="post: 2137718" data-attributes="member: 1521"><p>There are always direct reasons for pushing or pulling frictions to change. Luckily, it has no affect on actual bullet tension.</p><p>When we upsize with bullet seating the forces are higher than could be calculated as the bullet-base junction rolls brass outwards.</p><p>Our sizing is angular, and is most commonly seen when bushing neck sizing greater than 5thou in one step. This rolls brass inwards, beyond stamped on the bushing.</p><p>Anyway, while seating, that brass rolls outward and curves back onto the bullet bearing. It is a very slightly bowed grip. The greater the sizing, the greater the bowing energy added. If friction were normalized between, a 2nd seating(without that upsizing) would be way easier, but trust me on this: tension is still the same.</p><p>With either the 1st or 2nd seated bullets, having a slightly bowed grip, if you run a pull test the force can be higher than would be expected as the bow is taken out. It's a Chinese finger trap effect. It's not always what you have, but it does explain differences seen in past pull tests.</p><p></p><p>On friction alone, the only reason we should strive for reasonable seating force is for consistent CBTO (without a battle for it).</p><p>Greater/varied seating forces cause wedging changes with the seater plug on bullet noses.</p><p>It's ok to use a dry film lubricant in new necks. Other than moly, it won't change anything over a fired carbon layer, and won't affect MV.</p><p>Do not use a wet lube..</p><p>Moly does affect MV (lowers it), but this is NOT due to reduced friction. Moly is special in that it cools the charge with it's phase change.</p><p>A latent heat of vaporization, that other dry films do not introduce.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 2137718, member: 1521"] There are always direct reasons for pushing or pulling frictions to change. Luckily, it has no affect on actual bullet tension. When we upsize with bullet seating the forces are higher than could be calculated as the bullet-base junction rolls brass outwards. Our sizing is angular, and is most commonly seen when bushing neck sizing greater than 5thou in one step. This rolls brass inwards, beyond stamped on the bushing. Anyway, while seating, that brass rolls outward and curves back onto the bullet bearing. It is a very slightly bowed grip. The greater the sizing, the greater the bowing energy added. If friction were normalized between, a 2nd seating(without that upsizing) would be way easier, but trust me on this: tension is still the same. With either the 1st or 2nd seated bullets, having a slightly bowed grip, if you run a pull test the force can be higher than would be expected as the bow is taken out. It's a Chinese finger trap effect. It's not always what you have, but it does explain differences seen in past pull tests. On friction alone, the only reason we should strive for reasonable seating force is for consistent CBTO (without a battle for it). Greater/varied seating forces cause wedging changes with the seater plug on bullet noses. It's ok to use a dry film lubricant in new necks. Other than moly, it won't change anything over a fired carbon layer, and won't affect MV. Do not use a wet lube.. Moly does affect MV (lowers it), but this is NOT due to reduced friction. Moly is special in that it cools the charge with it's phase change. A latent heat of vaporization, that other dry films do not introduce. [/QUOTE]
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Neck tension and max bullet grip force
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