Range Report Fps guestimation
- Thread starter Dustoff82
- Start date
Factory (box) speed for Federal's 165 load is 2700 fps, out of a standard 24" test barrel. In that barrel length range, a fairly general estimate of the effect of length on velocity is anywhere from 15-25 fps per inch of barrel. Picking 20 fps (middle value) as the estimate would put you somewhere in the neighborhood of 2540 fps [2700 fps from a 24" barrel - (8"x20 fps/in)]. However, this is a very crude method for estimating and your actual velocity could realistically be anywhere from 2500 to 2600 fps.
Without having a chronograph, you can get a somewhat better idea of how fast they're moving by recording accurate drops at increasing distance. Get a good 100 yd zero, then measure the drop (or come up) at longer distance, preferably 300-400 yd or farther. Plug the numbers into a ballistic calculator with the appropriate atmospheric data, then adjust the MV value until the predicted drops match the actual as close as possible. The longer the distance, the larger the drops and therefore the the better the estimate by this method.
Without having a chronograph, you can get a somewhat better idea of how fast they're moving by recording accurate drops at increasing distance. Get a good 100 yd zero, then measure the drop (or come up) at longer distance, preferably 300-400 yd or farther. Plug the numbers into a ballistic calculator with the appropriate atmospheric data, then adjust the MV value until the predicted drops match the actual as close as possible. The longer the distance, the larger the drops and therefore the the better the estimate by this method.
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I do it that way,all the time. Chronos lie!
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