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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
BALLISTIC COEFFICIENTS/Twist Rates
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<blockquote data-quote="BryanLitz" data-source="post: 419278" data-attributes="member: 7848"><p>Lou,</p><p></p><p>I understand the approach your advocating, but disagree that it's the <em>right</em> approach for modeling ballistic trajectories for 99.9% of shooters.</p><p></p><p>To start, the difference between a trajectory modeled with BC referenced to the closest standard, and a trajectory modeled with the bullets unique drag curve will be less than 1 click thru the bullets supersonic range (which is where most shooters, and especially hunters are concerned).</p><p></p><p>When the bullet slows into the transonic speed range, stability becomes questionable and the trajectory becomes unpredictable as you said. However custom drag curves for each bullet will not solve that problem. You have atmospherics affecting stability in a way that indirectly affects the drag (induced drag) of the bullet, as well as the effects of different rifling patterns (depth, smoothness, # of riflings, etc become important when dealing with transonic stability). In other words, transonic flight is determined by way more than drag. Heck, most bullets just tumble at this speed, making any efforts to predict their trajectories impossible and irrelevant.</p><p></p><p>Am I correct in understanding your suggested way of 'predicting' a trajectory is to shoot your rifle and write down the drop?!?! Talk about Before Computers! Of course it's a good idea to verify your predicted drop just to be sure the theory matches reality, but don't forego the step of predicting the trajectory in the first place, it's quite useful! Plus you can't shoot in every condition (elevation, slant angle, wind, etc) so at some point you have to rely on a predictive model.</p><p></p><p>Using a good ballistic solver with accurate input data (including an accurate G7 BC) will result in trajectory predictions that are accurate within 1 click thru the supersonic range of the bullets flight. Below supersonic speeds, I agree, all bets are off. However I also understand that to actually predict trajectories thru the transonic speeds for most bullets requires aerodynamic models that are not available (or would take years and $100K's - doplar radar - to develop for each round) AND would only be relevant for a particular rifle barrel... All this to predict trajectories beyond what most have the accuracy to hit a vital zone anyway... I don't think that's a 'better' way.</p><p></p><p>Traditional BC's as we use them are very useful not just for comparing bullets to each other, but also for computing very accurate trajectories for the relevant flight envelope of the bullet.</p><p></p><p>-Bryan</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 419278, member: 7848"] Lou, I understand the approach your advocating, but disagree that it's the [i]right[/i] approach for modeling ballistic trajectories for 99.9% of shooters. To start, the difference between a trajectory modeled with BC referenced to the closest standard, and a trajectory modeled with the bullets unique drag curve will be less than 1 click thru the bullets supersonic range (which is where most shooters, and especially hunters are concerned). When the bullet slows into the transonic speed range, stability becomes questionable and the trajectory becomes unpredictable as you said. However custom drag curves for each bullet will not solve that problem. You have atmospherics affecting stability in a way that indirectly affects the drag (induced drag) of the bullet, as well as the effects of different rifling patterns (depth, smoothness, # of riflings, etc become important when dealing with transonic stability). In other words, transonic flight is determined by way more than drag. Heck, most bullets just tumble at this speed, making any efforts to predict their trajectories impossible and irrelevant. Am I correct in understanding your suggested way of 'predicting' a trajectory is to shoot your rifle and write down the drop?!?! Talk about Before Computers! Of course it's a good idea to verify your predicted drop just to be sure the theory matches reality, but don't forego the step of predicting the trajectory in the first place, it's quite useful! Plus you can't shoot in every condition (elevation, slant angle, wind, etc) so at some point you have to rely on a predictive model. Using a good ballistic solver with accurate input data (including an accurate G7 BC) will result in trajectory predictions that are accurate within 1 click thru the supersonic range of the bullets flight. Below supersonic speeds, I agree, all bets are off. However I also understand that to actually predict trajectories thru the transonic speeds for most bullets requires aerodynamic models that are not available (or would take years and $100K's - doplar radar - to develop for each round) AND would only be relevant for a particular rifle barrel... All this to predict trajectories beyond what most have the accuracy to hit a vital zone anyway... I don't think that's a 'better' way. Traditional BC's as we use them are very useful not just for comparing bullets to each other, but also for computing very accurate trajectories for the relevant flight envelope of the bullet. -Bryan [/QUOTE]
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