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Rifles, Reloading, Optics, Equipment
Reloading
Necking down 7mm STW to .257 STW
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<blockquote data-quote="Pdvdh" data-source="post: 1343708" data-attributes="member: 4191"><p>As Cheyenne has noted, large capacity .257 cartridges are prone to powder bridging when using extruded (stick) powders. It seems that the extruded powders jam up at the shoulder/case neck when the case neck diameter gets down to the .257 and smaller calibers. Kirby Allen identified this problem with his .257 Allen magnum. It causes very erratic case pressures when the powder dams up at the case neck. As a consequence, Kirby only uses and recommends ball powders in his .257 Allen Mag. Small diameter and short extruded powders might work? If you try 7828, I strongly advise the SSC version. </p><p></p><p>I own a .257 RUM, the 7mm RUM necked down to .257 which is very similar to Kirby's .257 Allen Magnum. I also experienced a few scary high pressure spikes with extruded powders. Live and learn... I now use Hodgdon US 869, a ball type powder. My case capacity is much greater than a 257 STW. I suggest you follow in Cheyenne's path. Use Ramshot.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 1343708, member: 4191"] As Cheyenne has noted, large capacity .257 cartridges are prone to powder bridging when using extruded (stick) powders. It seems that the extruded powders jam up at the shoulder/case neck when the case neck diameter gets down to the .257 and smaller calibers. Kirby Allen identified this problem with his .257 Allen magnum. It causes very erratic case pressures when the powder dams up at the case neck. As a consequence, Kirby only uses and recommends ball powders in his .257 Allen Mag. Small diameter and short extruded powders might work? If you try 7828, I strongly advise the SSC version. I own a .257 RUM, the 7mm RUM necked down to .257 which is very similar to Kirby's .257 Allen Magnum. I also experienced a few scary high pressure spikes with extruded powders. Live and learn... I now use Hodgdon US 869, a ball type powder. My case capacity is much greater than a 257 STW. I suggest you follow in Cheyenne's path. Use Ramshot. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Necking down 7mm STW to .257 STW
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