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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
257 Allen Magnum progress continues to another level...
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<blockquote data-quote="Fiftydriver" data-source="post: 132455" data-attributes="member: 10"><p><strong>Re: . In past tests the STW proved to produce about 47 fps more velocity p</strong></p><p></p><p>Blygy,</p><p></p><p>Its been up and running for a couple years not and is performing very well. It is a bit of a finicky round but it does have nearly a 100 gr capacity under a 1/4 more bore diameter!!!</p><p></p><p>Best loads I have tested have been with WC872 under a 156 gr ULD RBBT loaded to a comfortable 3300 fps. It will do near 3400 fps in a 30" pipe but there is no real good reason to do so other then shorten barrel life more then it already will be.</p><p></p><p>Have run into some issues with powder selection. Can only use the ultra slow burning Ball powders such as AA8700, US869 and WC872. Any stick powders, even if they are of appropriate burn rate will cause severe powder bridging issues and cause severe pressure spike.</p><p></p><p>With the slow ball powders the round performs very well and the heavier the bullets the better.</p><p></p><p>I tried to see if the 7mm RUM case necked down to 257 and fireformed would work with the 257 AM design but case capacity is simply to large being about 8-10 grains more powder volume then the original 338 RUM based 257 Allen Magnum. Performance was identical as far as velocity limits. Seems thats about the top of the pile for volume with a 25 cal bullet.</p><p></p><p>Kirby Allen(50)</p></blockquote><p></p>
[QUOTE="Fiftydriver, post: 132455, member: 10"] [b]Re: . In past tests the STW proved to produce about 47 fps more velocity p[/b] Blygy, Its been up and running for a couple years not and is performing very well. It is a bit of a finicky round but it does have nearly a 100 gr capacity under a 1/4 more bore diameter!!! Best loads I have tested have been with WC872 under a 156 gr ULD RBBT loaded to a comfortable 3300 fps. It will do near 3400 fps in a 30" pipe but there is no real good reason to do so other then shorten barrel life more then it already will be. Have run into some issues with powder selection. Can only use the ultra slow burning Ball powders such as AA8700, US869 and WC872. Any stick powders, even if they are of appropriate burn rate will cause severe powder bridging issues and cause severe pressure spike. With the slow ball powders the round performs very well and the heavier the bullets the better. I tried to see if the 7mm RUM case necked down to 257 and fireformed would work with the 257 AM design but case capacity is simply to large being about 8-10 grains more powder volume then the original 338 RUM based 257 Allen Magnum. Performance was identical as far as velocity limits. Seems thats about the top of the pile for volume with a 25 cal bullet. Kirby Allen(50) [/QUOTE]
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257 Allen Magnum progress continues to another level...
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