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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
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<blockquote data-quote="ricka0" data-source="post: 65249" data-attributes="member: 3086"><p>Hopefully the applied mathematician in me won't BIG TIME bore everyone to tears. I'm sure we are all aware that BC is dynamic, not a single number, ie it depends on Velocity.</p><p></p><p>When folks talk about using <strong><font color="red"> a </strong><font color="black">chronograph to get the BC, I hope they mean using <strong><font color="red"> a PAIR </strong><font color="black">of chronographs unless they are doing the correct statistics (which means you would need a lot of measurements too unless you have an exceptionally low StdDev in velocity). I believe Doppler radar is the preferred method to accurately get BC.</p><p></p><p><strong>[ QUOTE ]</strong></p><p> <strong></strong></p><p><strong><font color="red"></strong></p><p> <strong>Everything and anything affects this number. These are just a few bc tweekers: </strong></p><p><strong></strong></p><p><strong></strong></p><p></p><p>[/ QUOTE ] <font color="black"></p><p></p><p>Actually, the only things that effect BC are physical, ie topology (shape, defects) . axial symmetry, density and velocity. the new list</p><p><ul type="square">[*]barrel condition</p><p>[*]bullet bearing surface</p><p>[*]bullet meplats</p><p>[*]bullet dings/scratches</p><p>[*]Weight of individual bullet</p><p>[/list]</p><p></p><p>The following factors only change effective BC, not actual standardized BC. IE, these are environmental factors that effect bullet flight but have impact on corrected BC – ie if you corrected for these factors, then tested the bullets at Std Temp, pressure, Humidity, (I believe Altitude can be rolled into pressure), wind vector – you would get the same BC value. If you moved to another pressure/temp/humidity location you would still get the same BC.</p><p></p><p>Twist can also be corrected for sans sub stabilization. If you know the true BC, ballistics can accurately calculate the Velocity, [de]Acceleration, position at any position or point in time - pre subsonic. Precipitation could be corrected for but it would probably be too difficult to accurately quantify rain/ice conditions.</p><p></p><p>Properties that effect perceived BC but not actual Standardized BC</p><p><ul type="square">[*]Humidity</p><p>[*]barometric pressure</p><p>[*]air density/altitude</p><p>[*]temperature</p><p>[*]wind direction</p><p>[*]wind speed</p><p>[/list]</p><p></p><p><strong>[ QUOTE ]</strong></p><p> <strong></strong></p><p><strong><font color="red"></strong></p><p><strong>There can never be two bullets in the same box with exactly the same bc.</strong></p><p><strong></strong></p><p></p><p>[/ QUOTE ] <font color="black"></p><p></p><p>Perhaps if you want to get into quantum physics but given a large enough batch you could find identical BC bullets <strong><font color="red"> within the bounds of your measuring tolerance </strong> <font color="black"></p><p></p><p>That is where Standard Deviation comes in. If you know the Std Dev of a batch, you know expected variation. If you further add extreme spread, you know everything.</p><p></p><p>I'm not flaming or picking on you goodGrouper – I respect the awesome work/shooting/experience/info you bring to this forum. I hope to some day get 90% of the results you are getting today.</p></blockquote><p></p>
[QUOTE="ricka0, post: 65249, member: 3086"] Hopefully the applied mathematician in me won’t BIG TIME bore everyone to tears. I’m sure we are all aware that BC is dynamic, not a single number, ie it depends on Velocity. When folks talk about using [b]<font color="red"> a [/b]<font color="black">chronograph to get the BC, I hope they mean using [b]<font color="red"> a PAIR [/b]<font color="black">of chronographs unless they are doing the correct statistics (which means you would need a lot of measurements too unless you have an exceptionally low StdDev in velocity). I believe Doppler radar is the preferred method to accurately get BC. [b][ QUOTE ] <font color="red"> Everything and anything affects this number. These are just a few bc tweekers: [/b] [/ QUOTE ] <font color="black"> Actually, the only things that effect BC are physical, ie topology (shape, defects) . axial symmetry, density and velocity. the new list <ul type="square">[*]barrel condition [*]bullet bearing surface [*]bullet meplats [*]bullet dings/scratches [*]Weight of individual bullet [/list] The following factors only change effective BC, not actual standardized BC. IE, these are environmental factors that effect bullet flight but have impact on corrected BC – ie if you corrected for these factors, then tested the bullets at Std Temp, pressure, Humidity, (I believe Altitude can be rolled into pressure), wind vector – you would get the same BC value. If you moved to another pressure/temp/humidity location you would still get the same BC. Twist can also be corrected for sans sub stabilization. If you know the true BC, ballistics can accurately calculate the Velocity, [de]Acceleration, position at any position or point in time - pre subsonic. Precipitation could be corrected for but it would probably be too difficult to accurately quantify rain/ice conditions. Properties that effect perceived BC but not actual Standardized BC <ul type="square">[*]Humidity [*]barometric pressure [*]air density/altitude [*]temperature [*]wind direction [*]wind speed [/list] [b][ QUOTE ] <font color="red"> There can never be two bullets in the same box with exactly the same bc. [/b] [/ QUOTE ] <font color="black"> Perhaps if you want to get into quantum physics but given a large enough batch you could find identical BC bullets [b]<font color="red"> within the bounds of your measuring tolerance [/b] <font color="black"> That is where Standard Deviation comes in. If you know the Std Dev of a batch, you know expected variation. If you further add extreme spread, you know everything. I’m not flaming or picking on you goodGrouper – I respect the awesome work/shooting/experience/info you bring to this forum. I hope to some day get 90% of the results you are getting today. [/QUOTE]
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