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Rifles, Reloading, Optics, Equipment
Reloading
Why Hammer Bullets Are Always Faster
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<blockquote data-quote="nralifer" data-source="post: 3043239" data-attributes="member: 94556"><p>It seems intuitive that reduction of bearing surface through the use of multiple groves should improve MV. This effect of reduced friction should be seen with virtually any powder. That is exactly what I thought before doing the testing. The result was quite different. Repeated the test three times. The point was not necessarily to demonstrate superiority of one bullet over the other, but rather to see if reduced friction resulted in higher velocity. It did not. I welcome anyone to repeat this test. The multiple groves along the shank do have a potential penalty and that is to increase skin drag and thus reduce BC. We have known that for many years. Our early BC testing of prototype bullets with multiple groves showed that we were not obtaining the BCs we wanted. It wasn't until I found a Schlieren image of a bullet that had a crimp grove showing a shockwave from it that I realized that changes in surface curvature increased resistance to air passage creating shockwaves at supersonic speeds. When we minimized the groves and made the one or two groves more aerodynamic did we easily get the BCs we wanted. The current generation of bullets have one grove to break up the bearing surface more to prevent copper fouling than increasing MV.</p></blockquote><p></p>
[QUOTE="nralifer, post: 3043239, member: 94556"] It seems intuitive that reduction of bearing surface through the use of multiple groves should improve MV. This effect of reduced friction should be seen with virtually any powder. That is exactly what I thought before doing the testing. The result was quite different. Repeated the test three times. The point was not necessarily to demonstrate superiority of one bullet over the other, but rather to see if reduced friction resulted in higher velocity. It did not. I welcome anyone to repeat this test. The multiple groves along the shank do have a potential penalty and that is to increase skin drag and thus reduce BC. We have known that for many years. Our early BC testing of prototype bullets with multiple groves showed that we were not obtaining the BCs we wanted. It wasn’t until I found a Schlieren image of a bullet that had a crimp grove showing a shockwave from it that I realized that changes in surface curvature increased resistance to air passage creating shockwaves at supersonic speeds. When we minimized the groves and made the one or two groves more aerodynamic did we easily get the BCs we wanted. The current generation of bullets have one grove to break up the bearing surface more to prevent copper fouling than increasing MV. [/QUOTE]
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Why Hammer Bullets Are Always Faster
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