
Centerfire Rifles  Semiautomatic or Gas Operated Centerfire rifles, carbines and other gas operated rifles. 

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#1




Ballistic Coefficients: G1 vs G7
I just wanted to share an explanation of why some bullet manufacturers publish multiple ballistic coefficients of the same bullet for different velocity ranges.
Here's what Brian Litz of Berger Bullets has to say: Quote:
A typical bullet that closely matches the G1 profile and needs only one G1 BC to describe its drag characteristics across a wide velocity range: The standard G7 projectile profile: A typical bullet that closely matches the G7 profile and needs only one G7 BC to describe its drag characteristics across a wide velocity range: Quote:
When you choose the right drag model, one BC value describes the bullet's flight path from start to finish. 
#2




Great inanutshell summation Jimmy!
Folks, when shooting long range, one should use the BC that fits their bullet's profile. For nearly all of the long range projectiles that means using the G7 for calculations. For example: Lets look at a .308 launching the 175 SMK at 2500 FPS. Using G1 BC: AT 1000 yards we get about 41.9 MOA or 438.4 inches of drop with a retained velocity of about 1187 FPS. Using the G7 BC (more accurate data): At 1000 yards we get 43.3 MOA or 453 inches of drop with a retained velocity of about 1098. That is subsonic at sea level. The difference is important. If you were basing your data on the G1 you would think you are fine for 1000 yards; however, if you based your data on the G7 BC, you would know that 2500 fps is a little too slow for 1000 yards at sea level by only a few FPS. Yes, it is that important! If you are wondering why many manufactures publish only the G1 BC, it is because the G1 is a larger number and posting the G7 (always a lower number) will, most likely, confuse the prospective buyer who does not understand the difference. Last edited by RugerNo1; 10252011 at 10:25 AM.. Reason: can not spell or grammar :) 
#3




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