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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Questions about Ballistic FTE
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<blockquote data-quote="groper" data-source="post: 488911" data-attributes="member: 12550"><p>No, FTE is brilliant - i use it myself...</p><p></p><p>FTE doesnt know how to average the BC, you have to give it the averaged BC in the input. No ballistic calculator can average the BC automatically as it does not have all the information it needs in order to be able to do this.</p><p></p><p> Different shape bullets and their relationship with BC velocity dependence, vary at different rates due to their aerodynamic shape and mass.</p><p>So if we have bullet A - with a BC of say 0.5 @ 3000fps and BC of 0.4 @ 2000fps... </p><p>this doesnt mean that bullet B, still with a BC of 0.5 @ 3000fps, will have the same BC as bullet A @ 2000fps... bullet B might be 0.3 @ 2000fps.... so the decay rate is variable from bullet to bullet.</p><p></p><p>in other words, the BC velocity dependence is unique to every single different bullet. So unless the ballistic computer can recognize a multiple velocity bracketed G1 BC system - such as sierra quotes for their bullets as a means of helping this very dilemma- then you have to derive an averaged number yourself or obtain the averaged number from someone else who has hopefully done it accurately for that bullet, in order to have the best fitting trajectory prediction curve possible.</p><p></p><p>This is the service Bryan Litz provides, and he provides it in an averaged G7 BC format for long range bullets (which we are most interested in) as G7 is much less velocity dependent than G1, the drag curve fits better to long range bullets, and provides a much more accurate trajectory prediction when used in a ballistic calculator. This is a useful service because manufuacturer muzzle velocity BC`s are useless for anything but a rough comparison of bullets -as in which bullet might have lower drag than another, and of course a selling point for marketing purposes.</p><p></p><p>When long range shooters talk about BC and its use in trajectory prediction, what we are really talking about is "cumulatively averaged BC" sometimes referred to as "real world BC", not whats written on the box of bullets...</p></blockquote><p></p>
[QUOTE="groper, post: 488911, member: 12550"] No, FTE is brilliant - i use it myself... FTE doesnt know how to average the BC, you have to give it the averaged BC in the input. No ballistic calculator can average the BC automatically as it does not have all the information it needs in order to be able to do this. Different shape bullets and their relationship with BC velocity dependence, vary at different rates due to their aerodynamic shape and mass. So if we have bullet A - with a BC of say 0.5 @ 3000fps and BC of 0.4 @ 2000fps... this doesnt mean that bullet B, still with a BC of 0.5 @ 3000fps, will have the same BC as bullet A @ 2000fps... bullet B might be 0.3 @ 2000fps.... so the decay rate is variable from bullet to bullet. in other words, the BC velocity dependence is unique to every single different bullet. So unless the ballistic computer can recognize a multiple velocity bracketed G1 BC system - such as sierra quotes for their bullets as a means of helping this very dilemma- then you have to derive an averaged number yourself or obtain the averaged number from someone else who has hopefully done it accurately for that bullet, in order to have the best fitting trajectory prediction curve possible. This is the service Bryan Litz provides, and he provides it in an averaged G7 BC format for long range bullets (which we are most interested in) as G7 is much less velocity dependent than G1, the drag curve fits better to long range bullets, and provides a much more accurate trajectory prediction when used in a ballistic calculator. This is a useful service because manufuacturer muzzle velocity BC`s are useless for anything but a rough comparison of bullets -as in which bullet might have lower drag than another, and of course a selling point for marketing purposes. When long range shooters talk about BC and its use in trajectory prediction, what we are really talking about is "cumulatively averaged BC" sometimes referred to as "real world BC", not whats written on the box of bullets... [/QUOTE]
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