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<blockquote data-quote="Pdvdh" data-source="post: 2271775" data-attributes="member: 4191"><p>The SAAMI 280 Ackley Improved is the only SAAMI adopted cartridge I know of that has Ackley in it's name and has a different headspace than PO Ackley's version would have.</p><p></p><p>I don't know if Tikka bolt faces are cut to different diameters for the 243, 270, 280, and 30-06 cartridge chamberings. But with the Tikka style extractor, there is some latitude in cartridge case head/rim diameters that will still allow reliable extraction of fired cartridges. I don't think a case head 0.005" smaller than the machined bolt face will cause any extraction problems.</p><p></p><p>I think your primary question is, can SAAMI 280 Ackley Improved headstamped casings be safely fireformed for use in an original 280 A.I. chamber with the 0.014" deeper headspace? Yes, they could be provided a technique is used to hold the SAAMI headstamped cartridge case head in firm contact with the bolt face during fireforming. </p><p></p><p>The two most common methods used are: </p><p>1) seat a bullet into the case neck so the ogive of the bullet is firmly jammed into the rifling so the bolt closes with some crush fit force on the casing being fireformed. The bullet being tightly jammed into the lands of the rifling will force the case head firmly against the bolt face. This will prevent the case web from stretching and thinning during fire forming. The powder charge used for this fireforming should be reduced ~15% below maximum book powder vharge weight for the bullet weight being fired, as jamming the bullet against the lands will increase pressure compared to loading the same bullet off the lands the common distance of 0.010" to 0.020";</p><p>2) expand the SAAMI headstamped case necks to .308 inner diameter using a case neck expanding mandrel. Then resize the case neck back down to accept the .284" diameter bullet, BUT leave enough of the .308 diameter neck to create a shoulder that butts against the chamber shoulder, and holds the case head in firm contact with the bolt face with the bolt closed on the casing. Then load a fireforming load using eirher Cream of Wheat, or load a bullet and fire the cartridge to blow the case shoulder forward the 0.014" to match the deeper 280 A.I. chamber headspace.</p><p></p><p>Once the cases have been fireformed, the case shoulders should have expanded forward 0.014" and can then be loaded normally for the useful life of the casings. </p><p></p><p>If you use fireforming method 2, I recommend annealing the case necks after fireforming... Because expanding the case necks up to .308 diameter and then resizing the necks back down to .284 will work harden the case necks a bunch.</p></blockquote><p></p>
[QUOTE="Pdvdh, post: 2271775, member: 4191"] The SAAMI 280 Ackley Improved is the only SAAMI adopted cartridge I know of that has Ackley in it's name and has a different headspace than PO Ackley's version would have. I don't know if Tikka bolt faces are cut to different diameters for the 243, 270, 280, and 30-06 cartridge chamberings. But with the Tikka style extractor, there is some latitude in cartridge case head/rim diameters that will still allow reliable extraction of fired cartridges. I don't think a case head 0.005" smaller than the machined bolt face will cause any extraction problems. I think your primary question is, can SAAMI 280 Ackley Improved headstamped casings be safely fireformed for use in an original 280 A.I. chamber with the 0.014" deeper headspace? Yes, they could be provided a technique is used to hold the SAAMI headstamped cartridge case head in firm contact with the bolt face during fireforming. The two most common methods used are: 1) seat a bullet into the case neck so the ogive of the bullet is firmly jammed into the rifling so the bolt closes with some crush fit force on the casing being fireformed. The bullet being tightly jammed into the lands of the rifling will force the case head firmly against the bolt face. This will prevent the case web from stretching and thinning during fire forming. The powder charge used for this fireforming should be reduced ~15% below maximum book powder vharge weight for the bullet weight being fired, as jamming the bullet against the lands will increase pressure compared to loading the same bullet off the lands the common distance of 0.010" to 0.020"; 2) expand the SAAMI headstamped case necks to .308 inner diameter using a case neck expanding mandrel. Then resize the case neck back down to accept the .284" diameter bullet, BUT leave enough of the .308 diameter neck to create a shoulder that butts against the chamber shoulder, and holds the case head in firm contact with the bolt face with the bolt closed on the casing. Then load a fireforming load using eirher Cream of Wheat, or load a bullet and fire the cartridge to blow the case shoulder forward the 0.014" to match the deeper 280 A.I. chamber headspace. Once the cases have been fireformed, the case shoulders should have expanded forward 0.014" and can then be loaded normally for the useful life of the casings. If you use fireforming method 2, I recommend annealing the case necks after fireforming... Because expanding the case necks up to .308 diameter and then resizing the necks back down to .284 will work harden the case necks a bunch. [/QUOTE]
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