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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Attention wildcat bullet shooters!
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<blockquote data-quote="ricka0" data-source="post: 65253" data-attributes="member: 3086"><p>Kirby don't take offence, you know I'm your #1 Fan.</p><p>Drop charts are fine in you're always hunting at the same elevation/temp - But I'm using my 300 RUM (until you ship me my Kirby/Lilja 300 RUM /ubbthreads/images/graemlins/smile.gif ) for yotes outside Bakersfield CA - hot &amp; low altitude. Then I'll be using it for deer along the Missouri Breaks next fall ( 3,500 ft ) then moving to my cabin near showdown ski resort ( 7,400 ', cold ) - yotes/rabbits in goodGrouper s stomping grounds (santaquin UT ) - then on to the Nevada dessert.</p><p></p><p>I can't do a drop chart at each location, but once I <font color="red"> <strong>Calibrate</strong> </font> a ballistics model, I can move to any of these locations and very accurately compute drop.</p><p></p><p>If you want to use drop to approximate BC you can get more accurate results if your scope is exactly parallel with the bore.</p><p>A couple problems with using the drop approach is you need to know the Std Dev of velocity spread and BC to compute a BC #. IE, if bullet 1 has a BC of .700 and #2 has a BC of .710, then you get an inflated BC approximation. So you really need to know both Vel and BC to compute BC. This can actually be done by estimating the BC and using some statistics.</p><p></p><p>Getting the Velocity at two positions from one bullet gives you ZERO variation in BC and Velocity.</p><p>Wind, pressure, temp variation are also minimized.</p><p>I suppose you could do some non-trivial statistics to correct for these variations and use only the drop approach, but depending on the consistency of your groups this could involve many test shots. I need to think about how you would correct for two significant variables (vel &amp; BC) – You see the problem, bullet 2 has higher Vel but lower BC, bullet 3 has lower Vel but higher BC.</p><p></p><p>As my other hero goodGrouper eloquently pointed out BC changes from bullet to bullet, minute to minute. ( I think he left out barrel temp )</p></blockquote><p></p>
[QUOTE="ricka0, post: 65253, member: 3086"] Kirby don't take offence, you know I'm your #1 Fan. Drop charts are fine in you're always hunting at the same elevation/temp - But I'm using my 300 RUM (until you ship me my Kirby/Lilja 300 RUM [img]/ubbthreads/images/graemlins/smile.gif[/img] ) for yotes outside Bakersfield CA - hot & low altitude. Then I'll be using it for deer along the Missouri Breaks next fall ( 3,500 ft ) then moving to my cabin near showdown ski resort ( 7,400 ', cold ) - yotes/rabbits in goodGrouper s stomping grounds (santaquin UT ) - then on to the Nevada dessert. I can't do a drop chart at each location, but once I <font color="red"> [b]Calibrate[/b] </font> a ballistics model, I can move to any of these locations and very accurately compute drop. If you want to use drop to approximate BC you can get more accurate results if your scope is exactly parallel with the bore. A couple problems with using the drop approach is you need to know the Std Dev of velocity spread and BC to compute a BC #. IE, if bullet 1 has a BC of .700 and #2 has a BC of .710, then you get an inflated BC approximation. So you really need to know both Vel and BC to compute BC. This can actually be done by estimating the BC and using some statistics. Getting the Velocity at two positions from one bullet gives you ZERO variation in BC and Velocity. Wind, pressure, temp variation are also minimized. I suppose you could do some non-trivial statistics to correct for these variations and use only the drop approach, but depending on the consistency of your groups this could involve many test shots. I need to think about how you would correct for two significant variables (vel & BC) – You see the problem, bullet 2 has higher Vel but lower BC, bullet 3 has lower Vel but higher BC. As my other hero goodGrouper eloquently pointed out BC changes from bullet to bullet, minute to minute. ( I think he left out barrel temp ) [/QUOTE]
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