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Sandwarrior...
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Member Posts: 168,427 ✭
quote:Where ballistic coefficient really makes a difference is the 1000 yd. shooting. Where .2 better co-efficient can mean as much as 100 inches(velocity plays in here also) of difference in how much a bullet drops. So from about 300 yds on the BC just gets more and more important.
The closest I can come to comparing apples to apples is to run a program (JBM trajectory) to show the differences. I used a 180 gr. 7mm Berger VLD with a BC of .699 and Sierra's well known .308 168gr HPBT. Both fired at 2600 fps. standard seal level pressure and temp.
The Berger drops 336 inches @1000 yds. and drifts 65 inches in a 10 mph wind.
The Sierra drops 465 inches and drifts 124" in the same wind.
Reverse the bullet weights and use a 7mm(.284) Berger 168 gr.(BC= .649) @2600 fps. std cond. and the drop is 349" and 72" of windage with a 10 mph wind. The .308 Sierra HPBT 180 gr. bullet (BC=.493)travelling the same speed drops 416" and drifts 103" in a ten mile an hour wind. So you can see how important BC is in the long run. -good luck with this project.
Have you run this same test with the same caliber and different pills of the same weight, but with different BC's??? For example: say a .308 180 grain Nosler BT versus a 180 gr Partition Spitzer or protected point. (BC's of .507, .474, .361.) I would think that this would give you more accurate results.?.?
Thanks!
The closest I can come to comparing apples to apples is to run a program (JBM trajectory) to show the differences. I used a 180 gr. 7mm Berger VLD with a BC of .699 and Sierra's well known .308 168gr HPBT. Both fired at 2600 fps. standard seal level pressure and temp.
The Berger drops 336 inches @1000 yds. and drifts 65 inches in a 10 mph wind.
The Sierra drops 465 inches and drifts 124" in the same wind.
Reverse the bullet weights and use a 7mm(.284) Berger 168 gr.(BC= .649) @2600 fps. std cond. and the drop is 349" and 72" of windage with a 10 mph wind. The .308 Sierra HPBT 180 gr. bullet (BC=.493)travelling the same speed drops 416" and drifts 103" in a ten mile an hour wind. So you can see how important BC is in the long run. -good luck with this project.
Have you run this same test with the same caliber and different pills of the same weight, but with different BC's??? For example: say a .308 180 grain Nosler BT versus a 180 gr Partition Spitzer or protected point. (BC's of .507, .474, .361.) I would think that this would give you more accurate results.?.?
Thanks!
Comments
Yes I have. Using 168 gr. Sierra 7mm and 168 gr. Berger 7mm out of both my 7x57 @2630 fps and my 7WSM @ 2840. The Sierra's typically dropped about 1-1/2"{forgot to specify-300 yds} more than the Berger at the lower speed. They typically dropped just over an inch more at 300 yds. at the higher speed. Beyond that the Sierra's fall lower and lower vs. the Bergers. To be fair though I think their BC is higher than what Sierra publishes. As they perform better than their .30 cal 168 gr. match counterparts of only .013 BC less at the same velocities. My tests are not exacting enough to publish but the results I usually find are that the thicker/shorter Sierra ogive falls off faster than do Bergers.
Which also goes back to the question of "Do Berger 7mm 168's really have a .649 BC.?" Again, my lack of exacting scientific testing precludes saying so But I would say it's close. -hope that helps