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Hunting
The Basics, Starting Out
Bullet weight selection
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<blockquote data-quote="muleystalker" data-source="post: 1692428" data-attributes="member: 79944"><p>Here is an example of how faster velocity for a given bullet doesn't have that big of affect on the required twist for that bullet as most people think. The parameters for this sample are all the same except the velocity was changed. A change in altitude has way more affect than adding velocity. There is only a 0.05 difference in SG for a 400fps change in velocity.</p><p></p><p> Bullet:100gr .243 Badlands Bulldozer</p><p> BC:G1 0.575</p><p> Length: 1.430"</p><p> Twist: 1:7.5"</p><p> Temp: 59*</p><p> Altitude:0'</p><p> velocity; 3000fps</p><p>SG (gyroscopic stability) is a 1.07 Which is right at the unstable to marginal on Berger's barrel twist calculator.</p><p></p><p>Using the same above bullet and all the above perimeters only changing the velocity to</p><p>3400fps you get an SG of 1.12 , that is only a 0.05 change on the stability scale for a 400fps change in velocity.</p><p></p><p>For reference the SG scale is:</p><p></p><p>0------------------1.0|1.0-------------------1.5| 1.5---------------------greater</p><p> ------ unstable------|------marginal-----------|-----------stable---------------</p></blockquote><p></p>
[QUOTE="muleystalker, post: 1692428, member: 79944"] Here is an example of how faster velocity for a given bullet doesn't have that big of affect on the required twist for that bullet as most people think. The parameters for this sample are all the same except the velocity was changed. A change in altitude has way more affect than adding velocity. There is only a 0.05 difference in SG for a 400fps change in velocity. Bullet:100gr .243 Badlands Bulldozer BC:G1 0.575 Length: 1.430" Twist: 1:7.5" Temp: 59* Altitude:0' velocity; 3000fps SG (gyroscopic stability) is a 1.07 Which is right at the unstable to marginal on Berger's barrel twist calculator. Using the same above bullet and all the above perimeters only changing the velocity to 3400fps you get an SG of 1.12 , that is only a 0.05 change on the stability scale for a 400fps change in velocity. For reference the SG scale is: 0------------------1.0|1.0-------------------1.5| 1.5---------------------greater ------ unstable------|------marginal-----------|-----------stable--------------- [/QUOTE]
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The Basics, Starting Out
Bullet weight selection
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