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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Shoulder Design Discussion?
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<blockquote data-quote="Ken Howell" data-source="post: 22097" data-attributes="member: 23"><p>"First does the radius shoulder of a Weatherby really improve efficiency?"</p><p></p><p>No. That old "Powell-Miller Venturi Freebore" (PMVF) shoulder was pretty well discredited before Roy Weatherby became enamored of it and made it a sort of Weatherby trade mark. It has no positive ballistic value that anyone has been able to substantiate.</p><p></p><p>"Or is the added velocity just the extra powder space this design affords?"</p><p></p><p>No again. The extra velocity is a result of VERY high pressures in the factory loads. (Long story is too long for here. Suffice to say, I'm privy to some frightening inside-the-industry information that I can't publish without betraying confidences and possibly costing some good people their jobs.)</p><p></p><p>"Also if Ackley always liked 40 degrees why are factory rounds usually 30 or 35?"</p><p></p><p>Ackley did NOT always use the 40° shoulder. I haven't run the numbers, but I seem to remember that he used 28° shoulders at least as often if not more often than he used the 40° shoulder.</p><p></p><p>"What do you gain with the 40 degree besides increased powder capacity?"</p><p></p><p>Other problems are what you "gain" -- and not enough more powder capacity to be worth the trouble and expense (assuming loads with the same pressure levels in the same cases but with 25°, 30°, and 40° shoulders).</p><p></p><p>The manufacturers don't like having to make cases with shoulders steeper than 25°, and the maximum shoulder angle for relatively trouble-free handloadling seems to be 30°.</p><p></p><p>[ 03-05-2002: Message edited by: Ken Howell ]</p></blockquote><p></p>
[QUOTE="Ken Howell, post: 22097, member: 23"] "First does the radius shoulder of a Weatherby really improve efficiency?" No. That old "Powell-Miller Venturi Freebore" (PMVF) shoulder was pretty well discredited before Roy Weatherby became enamored of it and made it a sort of Weatherby trade mark. It has no positive ballistic value that anyone has been able to substantiate. "Or is the added velocity just the extra powder space this design affords?" No again. The extra velocity is a result of VERY high pressures in the factory loads. (Long story is too long for here. Suffice to say, I'm privy to some frightening inside-the-industry information that I can't publish without betraying confidences and possibly costing some good people their jobs.) "Also if Ackley always liked 40 degrees why are factory rounds usually 30 or 35?" Ackley did NOT always use the 40° shoulder. I haven't run the numbers, but I seem to remember that he used 28° shoulders at least as often if not more often than he used the 40° shoulder. "What do you gain with the 40 degree besides increased powder capacity?" Other problems are what you "gain" -- and not enough more powder capacity to be worth the trouble and expense (assuming loads with the same pressure levels in the same cases but with 25°, 30°, and 40° shoulders). The manufacturers don't like having to make cases with shoulders steeper than 25°, and the maximum shoulder angle for relatively trouble-free handloadling seems to be 30°. [ 03-05-2002: Message edited by: Ken Howell ] [/QUOTE]
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Shoulder Design Discussion?
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