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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
224 Allen Magnum testing finished............
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<blockquote data-quote="brianwinzor" data-source="post: 114228" data-attributes="member: 1067"><p>Kirby, Perhaps I should have re worded my post, but I am not expecting to achieve 3350 fps with the 257 Weatherby or later on in the shortened 7mm RUM. I meant to convey that my decision to switch to the 156 grain ULD from the 142 ULD was based on your experience with the bullet, and that you were able to use it successfully in your 257 AM at velocities up to about 3,350 fps. </p><p></p><p>I did some preliminary case capacity experiments and found that the new Norma 257 Weatherby brass (2.545 inches) held 87.8 grains of H870.</p><p></p><p>The new 7mm RUM cases (2.845 inches)held 114.5 grains of H870, and about 109.0 grains to the base of the neck. I estimated by filling the case to different levels, that to get about 90.0 grains of H870 occupying to the base of the neck, I would have to shorten the case to about 2.475 inches, assuming that I maintained the same shoulder angle and neck length.</p><p></p><p>At this stage I intend to chronograph and accuracy test the 125, 142, and 156 grain bullets in the 257 Weatherby, and use it in the field for about 12 months, then make an assessment of what the end capacity of my shortened 25/7mm RUM should be. </p><p></p><p>The complicating factor in making that assessment is that Norma brass has a reputation for being soft in the head, and that the 7mm RUM brass of equal capacity may show less pressure. </p><p></p><p>The other factor for consideration is available powders here in Oz that are likely to enable me to achieve 95 - 100% loading density at maximum pressure with the 156 grain bullet. I currently have a supply of H870, but the only local powder is AR 2218 (H50BMG in US). However, earlier this week I spoke to the Vihtavouri distributor, and if I order at least 3kg (6.6lbs) I could get some 20N29 included in his next shipment, which would be about 12 months away.</p><p></p><p>I would like the 25/7mm RUM short to be able to achieve at least 3,150 fps in the 26 inch Krieger barrel, if the 257 Weatherby can achieve 3,000 fps. It will be interesting to see if that can be achieved. Regards, Brian.</p></blockquote><p></p>
[QUOTE="brianwinzor, post: 114228, member: 1067"] Kirby, Perhaps I should have re worded my post, but I am not expecting to achieve 3350 fps with the 257 Weatherby or later on in the shortened 7mm RUM. I meant to convey that my decision to switch to the 156 grain ULD from the 142 ULD was based on your experience with the bullet, and that you were able to use it successfully in your 257 AM at velocities up to about 3,350 fps. I did some preliminary case capacity experiments and found that the new Norma 257 Weatherby brass (2.545 inches) held 87.8 grains of H870. The new 7mm RUM cases (2.845 inches)held 114.5 grains of H870, and about 109.0 grains to the base of the neck. I estimated by filling the case to different levels, that to get about 90.0 grains of H870 occupying to the base of the neck, I would have to shorten the case to about 2.475 inches, assuming that I maintained the same shoulder angle and neck length. At this stage I intend to chronograph and accuracy test the 125, 142, and 156 grain bullets in the 257 Weatherby, and use it in the field for about 12 months, then make an assessment of what the end capacity of my shortened 25/7mm RUM should be. The complicating factor in making that assessment is that Norma brass has a reputation for being soft in the head, and that the 7mm RUM brass of equal capacity may show less pressure. The other factor for consideration is available powders here in Oz that are likely to enable me to achieve 95 - 100% loading density at maximum pressure with the 156 grain bullet. I currently have a supply of H870, but the only local powder is AR 2218 (H50BMG in US). However, earlier this week I spoke to the Vihtavouri distributor, and if I order at least 3kg (6.6lbs) I could get some 20N29 included in his next shipment, which would be about 12 months away. I would like the 25/7mm RUM short to be able to achieve at least 3,150 fps in the 26 inch Krieger barrel, if the 257 Weatherby can achieve 3,000 fps. It will be interesting to see if that can be achieved. Regards, Brian. [/QUOTE]
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224 Allen Magnum testing finished............
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