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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Understanding cartridge efficiency
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<blockquote data-quote="P7M13" data-source="post: 1914186" data-attributes="member: 94154"><p>Long winded, and forgive me if you already know this.</p><p>As a reloader, cartridge<strong><em> efficacy </em></strong>is what gives me the best brass life, minimal maintenance, and outstanding performance. Some of the things that enable that are 35° or 40° shoulders, long enough necks for good bullet seating and minimal runout, slight taper for easier extraction without increasing rearward force on the bolt face, excellent magazine fit and feed capability, etc. These are many of the things that P.O. Ackley did in his case modification experiments.</p><p>An internal ballistician can tell you about efficiency. Borrowing a page from the Manhattan Project, if you really wanted to maximize the efficiency of your cartridge, you would "shape" the powder charge and load the cartridge with layers of powders of different burn rates and charge densities, focusing the shock wave. Problem is, you'd probably pulverize the bullet before it even left the chamber. Bullets are cheap. Quantity thereof and the quality of their use tends to win.</p><p></p><p>Seems to me, in your thirst for efficiency knowledge, you are asking about same powder charge, same bullet, different velocities. You may well know, the only way to test this would be same barrel/powder/bullet etc. I read posts here and on other forums where people are loading cartridges like 338 LM with the same powder, charge, bullet weight, primer and brass that I use, in a barrel 2" longer, and they're getting 200 FPS <strong><em>more</em></strong> muzzle velocity than I do. I scratch my head and wonder, WTH am I doing wrong? Mind you, their rig might be a Defiance action with Krieger or Shilen barrel, same twist and mine is a Savage 110BA. So, no matter what the cartridge might be capable of, YMMV.</p><p>All that said, I offer this comparison of 7mm Cartridges, the first two with similar case capacities, for your review:</p><p></p><p>[ATTACH=full]196530[/ATTACH]</p></blockquote><p></p>
[QUOTE="P7M13, post: 1914186, member: 94154"] Long winded, and forgive me if you already know this. As a reloader, cartridge[B][I] efficacy [/I][/B]is what gives me the best brass life, minimal maintenance, and outstanding performance. Some of the things that enable that are 35° or 40° shoulders, long enough necks for good bullet seating and minimal runout, slight taper for easier extraction without increasing rearward force on the bolt face, excellent magazine fit and feed capability, etc. These are many of the things that P.O. Ackley did in his case modification experiments. An internal ballistician can tell you about efficiency. Borrowing a page from the Manhattan Project, if you really wanted to maximize the efficiency of your cartridge, you would "shape" the powder charge and load the cartridge with layers of powders of different burn rates and charge densities, focusing the shock wave. Problem is, you'd probably pulverize the bullet before it even left the chamber. Bullets are cheap. Quantity thereof and the quality of their use tends to win. Seems to me, in your thirst for efficiency knowledge, you are asking about same powder charge, same bullet, different velocities. You may well know, the only way to test this would be same barrel/powder/bullet etc. I read posts here and on other forums where people are loading cartridges like 338 LM with the same powder, charge, bullet weight, primer and brass that I use, in a barrel 2" longer, and they're getting 200 FPS [B][I]more[/I][/B] muzzle velocity than I do. I scratch my head and wonder, WTH am I doing wrong? Mind you, their rig might be a Defiance action with Krieger or Shilen barrel, same twist and mine is a Savage 110BA. So, no matter what the cartridge might be capable of, YMMV. All that said, I offer this comparison of 7mm Cartridges, the first two with similar case capacities, for your review: [ATTACH type="full" alt="1591014081247.png"]196530[/ATTACH] [/QUOTE]
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Understanding cartridge efficiency
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