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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Let's argue about BC's
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<blockquote data-quote="groper" data-source="post: 475020" data-attributes="member: 12550"><p>Eddy, </p><p>Exbal cant handle G7 can it? But will it handle a multi G1 set?</p><p></p><p>this relates to exactly what i said earlier... when your shooting allen magnums with extremely high velocity, you will need to use a much higher G1 BC for the shorter ranges or first part of the trajectory than BL publishes... as i said, G1 BC is very velocity dependent - so very high velocity VLD bullets will exhibit much higher G1 BC`s whilst their speed is high... However, you will find that toward the end of the trajectory, at very long range when theyve had a chance to slow down, the bullet will impact much lower than predicted... The only way to combat this, is to input a lower BC for the slower part of its flight regime by way of a velocity bracketed G1 set like sierra publishes. </p><p></p><p>Whats interesting is that BL would have certainly given Paul a velocity bracketed set, not just a single G1 BC - Paul has chosen not to publish this it seems so we cant see how fast the G1 BC of his 7mm 200gr decays with velocity... He would have also given him a single G7 BC - because thats what Bryan does.</p><p></p><p>Remember, BL is giving us AVERAGE BC`s, for the flight regime in which he tested them. If he tested them from a very fast 7mm caliber such as a long barrelled allen mag or STW etc. then this would make the G1 numbers look much better on paper. If he tested them from a 7mm-08 or similar, then the G1 numbers would look much lower... </p><p></p><p>This is why BL so strongly believes in adopting the G7 system- because it wouldnt suffer from the same inconsistencies and require so many caveats when quoting the G1 BC - predominately - how fast the bullet is going, and how fast the BC decays from that point OR how much better it gets if your lucky enough to be able to shoot it very fast. G1 sux...</p><p></p><p>The G7 number also gets higher with more velocity, but by MUCH less than the G1. A single average G7 number, will give 99% of users a very good trajectory fit when you give your calc correct data on everything else (which isnt hard).</p><p></p><p>Lastly, if your using a Litz G7 number, and you dont have some exotic extremely fast or slow caliber, and your still having problems with your trajectory fit - then you pretty much are guaranteed to have errors in your other inputs or your chrony could be telling lies... Mr Litz is a professional, and his methods are very accurate, but he is not the aberdeen proving ground either so he cant give us BC`s to suit everyone, only 99% of us...</p></blockquote><p></p>
[QUOTE="groper, post: 475020, member: 12550"] Eddy, Exbal cant handle G7 can it? But will it handle a multi G1 set? this relates to exactly what i said earlier... when your shooting allen magnums with extremely high velocity, you will need to use a much higher G1 BC for the shorter ranges or first part of the trajectory than BL publishes... as i said, G1 BC is very velocity dependent - so very high velocity VLD bullets will exhibit much higher G1 BC`s whilst their speed is high... However, you will find that toward the end of the trajectory, at very long range when theyve had a chance to slow down, the bullet will impact much lower than predicted... The only way to combat this, is to input a lower BC for the slower part of its flight regime by way of a velocity bracketed G1 set like sierra publishes. Whats interesting is that BL would have certainly given Paul a velocity bracketed set, not just a single G1 BC - Paul has chosen not to publish this it seems so we cant see how fast the G1 BC of his 7mm 200gr decays with velocity... He would have also given him a single G7 BC - because thats what Bryan does. Remember, BL is giving us AVERAGE BC`s, for the flight regime in which he tested them. If he tested them from a very fast 7mm caliber such as a long barrelled allen mag or STW etc. then this would make the G1 numbers look much better on paper. If he tested them from a 7mm-08 or similar, then the G1 numbers would look much lower... This is why BL so strongly believes in adopting the G7 system- because it wouldnt suffer from the same inconsistencies and require so many caveats when quoting the G1 BC - predominately - how fast the bullet is going, and how fast the BC decays from that point OR how much better it gets if your lucky enough to be able to shoot it very fast. G1 sux... The G7 number also gets higher with more velocity, but by MUCH less than the G1. A single average G7 number, will give 99% of users a very good trajectory fit when you give your calc correct data on everything else (which isnt hard). Lastly, if your using a Litz G7 number, and you dont have some exotic extremely fast or slow caliber, and your still having problems with your trajectory fit - then you pretty much are guaranteed to have errors in your other inputs or your chrony could be telling lies... Mr Litz is a professional, and his methods are very accurate, but he is not the aberdeen proving ground either so he cant give us BC`s to suit everyone, only 99% of us... [/QUOTE]
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