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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Badlands Precision Bullets thread - From BC to terminal ballistics
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<blockquote data-quote="nralifer" data-source="post: 2628534" data-attributes="member: 94556"><p>Your instincts about gyroscopic stability are well placed. The recommended twist rates for the 205 SBD2 actually is 8.5. Both the aluminum tip and lower atmospheric pressure add stability, the former because the light tip makes the bullet behave more as a bullet of shorter length (usually about 0.100" shorter), and high altitude, causing lower station pressure (gyroscopic stability increases with lower station pressure). We quote a twist rate that will stabilize the BD2s at sea level, so that at higher altitudes stability will increase. Your idea of over stabilizing the bullet is sound. Stability factors above 2 are icing on the cake since at the over stabilization aids in the transitioning of the bullet to subsonic speed, something not necessary for hunting since the BD2s are are designed to open at 1700 fps impact velocity. </p><p>As to whether the added angular momentum (increased rpm of the bullet) adds to the terminal performance, a faster spin at impact certainly can't hurt, and may cause more liquefaction by the sharp petals after expansion aiding in penetration to some degree, how much though I can't tell you. Excellent question though.</p></blockquote><p></p>
[QUOTE="nralifer, post: 2628534, member: 94556"] Your instincts about gyroscopic stability are well placed. The recommended twist rates for the 205 SBD2 actually is 8.5. Both the aluminum tip and lower atmospheric pressure add stability, the former because the light tip makes the bullet behave more as a bullet of shorter length (usually about 0.100” shorter), and high altitude, causing lower station pressure (gyroscopic stability increases with lower station pressure). We quote a twist rate that will stabilize the BD2s at sea level, so that at higher altitudes stability will increase. Your idea of over stabilizing the bullet is sound. Stability factors above 2 are icing on the cake since at the over stabilization aids in the transitioning of the bullet to subsonic speed, something not necessary for hunting since the BD2s are are designed to open at 1700 fps impact velocity. As to whether the added angular momentum (increased rpm of the bullet) adds to the terminal performance, a faster spin at impact certainly can’t hurt, and may cause more liquefaction by the sharp petals after expansion aiding in penetration to some degree, how much though I can’t tell you. Excellent question though. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Badlands Precision Bullets thread - From BC to terminal ballistics
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