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Thread: Effective Rotational Spin.

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    Default Effective Rotational Spin.

    To most they don’t have a real interest in understanding Rotational Spin that is a separate force acting on a bullet once it leaves the bore. Well, my interest took hold to do a little exploring. I started examining a Twist Calculator and what it shows. Using the calculator with different velocities I learn what a barrel twist rate should be. Now the calculator only shows the slowest recommended twist needed to achieve a stable bullet flight with a specific velocity. In the example below I used 1300fps (250SW) and it shows I need a minimum of 1:27 twist for stable flight. When using this calculator and wanting to see the results for an all-copper bullet you need to adjust the Bullet SG value.
    So if you have any doubt having enough barrel twist or enough velocity this guide is a good reference.
    Once you input the values required you need to click on the blue bar.
    Last edited by ET1; September 25th, 2022 at 08:26 AM.

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