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California Precision Rifle Club California Precision Rifle Club Forum |
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#1
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Lower G7 BC at higher velocities? Experimental drag and G7 BC data for 175 SMK?
In the Litz book, Applied Ballistics for Long Range Shooting there is a section in the back that shows the drag and bc data for specific bullets and includes diagrams of the bullets. Can someone explain to me why it states that the G7 BC of 175 SMKs going at 3000fps(.240) is lower than at 2500 fps(.242)?
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#3
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Quote:
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Luck favors the prepared. The original battle plan did not survive initial contact with the enemy. "The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt |
#4
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Aerodynamics. As speed increases the shape (overall, frontal and BT) may not flow air as well as at the slower speed. Same as why the listed BC's are lower at lower velocity. The shape performs best within a specific range.
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Rob Thomas - Match Director NCPPRC Tactical Long Range Match Match Director Sac Valley Vintage Military Rifle Long Range Match |
#5
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yep.
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TEAM GAP, Shooter 7 GA Precision Yes, it's worth it. |
#6
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We're conditioned to think that 'BC degrades with velocity'. This is almost always true with the traditional G1 BC's because the drag curves mismatch so severely. In particular, the drag of most bullets grows in relation to the G1 standard below about 2000 fps.
However, since the G7 standard drag curve is so similar to most long range bullets, the drag curve of your particular bullet may be slightly above or below the G7 standard curve over a range of speeds. Because the curves ride so close together, you may find the BC increases or decreases slightly at various speeds. Of course when you're talking about 0.002 difference (less than 1%), it could very well be experimental noise Take care, -Bryan |
#8
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Bryan,
Thanks for the response. I get what you are saying. Really cool to have the author of the book respond in this thread. BTW, great book. I really enjoyed the parts about wind deflection and spin drift. |
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