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Trueing muzzle velocity vs BC
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<blockquote data-quote="nralifer" data-source="post: 2587203" data-attributes="member: 94556"><p>I tend to agree with you. Why change an accurately measured value assuming the lab radar is the most accurate way of measuring the MV. What none of us have considered are the individual factors that affect the drag coefficient. These are air density, compressibility, viscosity, and the direction of the air flow (wind direction and speed) relative to the bullet. We forget that over extended ranges these atmospheric factors can vary significantly. All one has to do to appreciate this variability is to take a bike ride on a calm evening over about a mile. You will notice how the air can feel at times cooler and warmer as you pass through it. These are thermal columns of air due to ground heat. The warmer columns are less dense than the cooler air, so it is reasonable to believe the drag on the bullet constantly varies along its path. The high powered radar can measure changes in velocity over very short distances, so with the proper computing power a BC for each increment of velocity change can be calculated. A predicted trajectory can be calculated from data gathered over say 10 shots which is a best fit for the ten shots. Each shot is unique since there are a multiplicity of atmospheric variables constantly changing in between shots and from day to day. That is why "truing" the BC makes more sense.</p></blockquote><p></p>
[QUOTE="nralifer, post: 2587203, member: 94556"] I tend to agree with you. Why change an accurately measured value assuming the lab radar is the most accurate way of measuring the MV. What none of us have considered are the individual factors that affect the drag coefficient. These are air density, compressibility, viscosity, and the direction of the air flow (wind direction and speed) relative to the bullet. We forget that over extended ranges these atmospheric factors can vary significantly. All one has to do to appreciate this variability is to take a bike ride on a calm evening over about a mile. You will notice how the air can feel at times cooler and warmer as you pass through it. These are thermal columns of air due to ground heat. The warmer columns are less dense than the cooler air, so it is reasonable to believe the drag on the bullet constantly varies along its path. The high powered radar can measure changes in velocity over very short distances, so with the proper computing power a BC for each increment of velocity change can be calculated. A predicted trajectory can be calculated from data gathered over say 10 shots which is a best fit for the ten shots. Each shot is unique since there are a multiplicity of atmospheric variables constantly changing in between shots and from day to day. That is why “truing” the BC makes more sense. [/QUOTE]
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