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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Excessive Throat Growth Question
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<blockquote data-quote="Bart B" data-source="post: 620882" data-attributes="member: 5302"><p>If cases last only 5 shots then primers start falling out, consider what's happening. Peak pressure's close to 65,000 CUP (81,000 PSI). Cartridge brass starts extruding between 60,000 and 65,000 CUP depending on its metal composition. Your cases are extruding 'cause they don't spring back to where they started in the primer pocket area. So, you have mistreated the barrel by firing ammo in it that's got too much peak pressure that not only shortened the normal barrel life for that cartridge. And you've also mistreated the cases. For a comparison, 7mm Rem. Mag. barrels that shot that accurate back when they were popular in prone long range matches lasted for that many rounds before opening up a noticable amount. And the Allen version burns a lot more powder. Allen's web site states this about their 7 Mag.: "Limited barrel life, cases somewhat involved to form, must use ultra slow burning ball powders." I'm surprised you got barrel life that long.</p><p></p><p>Such is life when folks are only happy operating their rifles with peak pressures in the small margin of safety range where cases and barrels don't last very long.</p></blockquote><p></p>
[QUOTE="Bart B, post: 620882, member: 5302"] If cases last only 5 shots then primers start falling out, consider what's happening. Peak pressure's close to 65,000 CUP (81,000 PSI). Cartridge brass starts extruding between 60,000 and 65,000 CUP depending on its metal composition. Your cases are extruding 'cause they don't spring back to where they started in the primer pocket area. So, you have mistreated the barrel by firing ammo in it that's got too much peak pressure that not only shortened the normal barrel life for that cartridge. And you've also mistreated the cases. For a comparison, 7mm Rem. Mag. barrels that shot that accurate back when they were popular in prone long range matches lasted for that many rounds before opening up a noticable amount. And the Allen version burns a lot more powder. Allen's web site states this about their 7 Mag.: "Limited barrel life, cases somewhat involved to form, must use ultra slow burning ball powders." I'm surprised you got barrel life that long. Such is life when folks are only happy operating their rifles with peak pressures in the small margin of safety range where cases and barrels don't last very long. [/QUOTE]
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Excessive Throat Growth Question
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