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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Short necks=short throat life??
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<blockquote data-quote="Brent" data-source="post: 58076" data-attributes="member: 99"><p>I know a smith who set up a test using a 6.5 WSM short neck, and another with a longer neck. The cases were formed with 300 Ultra Mag basic brass, so bodies were identical. </p><p></p><p>The throat was shot out in the short neck in 100 rounds, about .100 erosion, or .001 per round. </p><p></p><p>The longer neck was almost .400 in length and proved to have .007 erosion in about 700 rounds.</p><p></p><p>Highpower shooters tell me that the 300wm is a throat burner compared to most any other round they use. Not hard to understand though. They shoot fast, and is probably the most extreme abuse a barrel sees. They say 800-1200 rounds is it for the 300WM in highpower. The guys I know all opt for a longer neck, sharper shoulder, lower case capacity with medium to high BC bullets depending on range. </p><p></p><p>It is said that at the apex where the shoulder angle lines would intersect up in the neck area should be well below the case mouth, the further the better. This offers more physical protection, I believe, so the throat is not being directly sand blasted by the hot burning powder so much. There are formulas that determine what the optimal neck length is for a specific caliber and shoulder angle is, but a longer neck and sharper shoulder angle better keep this turbulance point inside the case neck.</p><p></p><p>One more point on another note is that a longer neck will offer support and better alignment to the bullet for a longer time so it is more fully engraved by the rifling before it is allowed to move a few ten thou off axis at the rear. Often a short neck case will not even allow the bullet to engrave before it laves the neck, especially on short bearing length bullets and ones seated further from the rifling. The larger diameter the throat is, the worse this is in my mind. We can turn necks to within a tenth or two of chamber dia, while most freebore throat diameters are about .0005 over bullet dia., so a neck that supports well will be better (and adjustable) off in controling the base of the bullet for best alignment.</p></blockquote><p></p>
[QUOTE="Brent, post: 58076, member: 99"] I know a smith who set up a test using a 6.5 WSM short neck, and another with a longer neck. The cases were formed with 300 Ultra Mag basic brass, so bodies were identical. The throat was shot out in the short neck in 100 rounds, about .100 erosion, or .001 per round. The longer neck was almost .400 in length and proved to have .007 erosion in about 700 rounds. Highpower shooters tell me that the 300wm is a throat burner compared to most any other round they use. Not hard to understand though. They shoot fast, and is probably the most extreme abuse a barrel sees. They say 800-1200 rounds is it for the 300WM in highpower. The guys I know all opt for a longer neck, sharper shoulder, lower case capacity with medium to high BC bullets depending on range. It is said that at the apex where the shoulder angle lines would intersect up in the neck area should be well below the case mouth, the further the better. This offers more physical protection, I believe, so the throat is not being directly sand blasted by the hot burning powder so much. There are formulas that determine what the optimal neck length is for a specific caliber and shoulder angle is, but a longer neck and sharper shoulder angle better keep this turbulance point inside the case neck. One more point on another note is that a longer neck will offer support and better alignment to the bullet for a longer time so it is more fully engraved by the rifling before it is allowed to move a few ten thou off axis at the rear. Often a short neck case will not even allow the bullet to engrave before it laves the neck, especially on short bearing length bullets and ones seated further from the rifling. The larger diameter the throat is, the worse this is in my mind. We can turn necks to within a tenth or two of chamber dia, while most freebore throat diameters are about .0005 over bullet dia., so a neck that supports well will be better (and adjustable) off in controling the base of the bullet for best alignment. [/QUOTE]
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Short necks=short throat life??
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