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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: 474804" data-attributes="member: 12550"><p>Paul,</p><p> You wont get any argument from me about shooting thru 2 chronies being a very accurate method of determining BC, but now im confused... If you were aware of accurate methods of determining BC, and practiced them, how did you not understand the reasons behind why Bryan revised your BC to .74 from 0.9?</p><p></p><p>I offered the acoustic method because its easy to setup... simply setup 1 Chrony at the muzzle and open up your laptop and start recording with its inbuilt mic for 1 string during your load development or whatever your shooting that day... When you get home, you can analyze the recording, do the math, and determine a real world G7 BC usually within 1% accuracy provided you payed careful attention to the details - namely wind vector, distances to the target are accurate enough with a decent laser rangefinder, measure the distance from your muzzle to the laptop within 1 ft, and air temperature.</p><p></p><p>But hey, if you dont mind the hassle to setup another chrony at the target, at long range and a shield for it, all the better... Both methods can give a VERY accurate BC result, PROVIDED you use a G7 BC calculation from the data.</p><p></p><p>However;</p><p>If you use the 2 chrony velocity method over short ranges, say 300yds for example (because we are lazy and cant be bothered setting up a shield in front of the chrony to do it at long range without risk of smashing our equipment) <em>then go and use the velocity data in a G1 calculation</em> - <strong>your only measuring the BC in the fastest part of its flight regime!- which will give you a higher G1 number than what is useful!!! </strong>The number you get, even tho its accurate, its only purpose will be to look good published on bullet boxs for marketing purposes...something us long range shooters grow tiresome of... If you must use G1 BC`s for your ballistics calculator, whether it doesnt have the G7 function inbuilt or the user is simply old fashioned, what we need is an AVERAGE G1 or multi velocity bracketed G1 number set, for it to be a real world and useful number that will give the user correct dope at extended ranges... <strong>which is the point, and is what meets the users needs</strong> - which is what Bryan gave us... Afterall, we barely even need to correct for elevation or wind at all inside 300yds of decent flat shooting caliber, so a G1 number for this part of the bullets flight regime is totally useless.</p><p></p><p>Be so much simpler if the entire industry would switch to quoting G7 numbers instead of the **** antiquated G1 crap...</p><p></p><p>Bryan Litz has done a great job in giving us the "real world" AVERAGE BC`s (over the entire 1000yd flight regime) that we actually NEED for so many bullets out there... any bullet maker who simply publishes the highest G1 BC at 3300fps - isnt doing any of us any favours, but it sure does keep Bryan busy sorting out the weed from the chaff...</p></blockquote><p></p>
[QUOTE="groper, post: 474804, member: 12550"] Paul, You wont get any argument from me about shooting thru 2 chronies being a very accurate method of determining BC, but now im confused... If you were aware of accurate methods of determining BC, and practiced them, how did you not understand the reasons behind why Bryan revised your BC to .74 from 0.9? I offered the acoustic method because its easy to setup... simply setup 1 Chrony at the muzzle and open up your laptop and start recording with its inbuilt mic for 1 string during your load development or whatever your shooting that day... When you get home, you can analyze the recording, do the math, and determine a real world G7 BC usually within 1% accuracy provided you payed careful attention to the details - namely wind vector, distances to the target are accurate enough with a decent laser rangefinder, measure the distance from your muzzle to the laptop within 1 ft, and air temperature. But hey, if you dont mind the hassle to setup another chrony at the target, at long range and a shield for it, all the better... Both methods can give a VERY accurate BC result, PROVIDED you use a G7 BC calculation from the data. However; If you use the 2 chrony velocity method over short ranges, say 300yds for example (because we are lazy and cant be bothered setting up a shield in front of the chrony to do it at long range without risk of smashing our equipment) [I]then go and use the velocity data in a G1 calculation[/I] - [B]your only measuring the BC in the fastest part of its flight regime!- which will give you a higher G1 number than what is useful!!! [/B]The number you get, even tho its accurate, its only purpose will be to look good published on bullet boxs for marketing purposes...something us long range shooters grow tiresome of... If you must use G1 BC`s for your ballistics calculator, whether it doesnt have the G7 function inbuilt or the user is simply old fashioned, what we need is an AVERAGE G1 or multi velocity bracketed G1 number set, for it to be a real world and useful number that will give the user correct dope at extended ranges... [B]which is the point, and is what meets the users needs[/B] - which is what Bryan gave us... Afterall, we barely even need to correct for elevation or wind at all inside 300yds of decent flat shooting caliber, so a G1 number for this part of the bullets flight regime is totally useless. Be so much simpler if the entire industry would switch to quoting G7 numbers instead of the **** antiquated G1 crap... Bryan Litz has done a great job in giving us the "real world" AVERAGE BC`s (over the entire 1000yd flight regime) that we actually NEED for so many bullets out there... any bullet maker who simply publishes the highest G1 BC at 3300fps - isnt doing any of us any favours, but it sure does keep Bryan busy sorting out the weed from the chaff... [/QUOTE]
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