The Firing Line Forums - View Single Post - Disaster with Barnes TSX in 257 Weatherby

FrankenMauser · October 30, 2012, 01:50 AM

In your photo, I don't see anything truly key-holing, but they may be yawing (still a stability issue).

Don't worry about the ballistic coefficients. They have far more to do with a bullet's flight characteristics, than stability. And, a bullet's shape affects the BC more than length alone.

Unrelated to the OP, but related to your last post....
Note how Sierra quotes multiple BCs for their bullets.
That's because G1 ballistic coefficients actually change significantly in flight (as velocity changes). And, the standard G1 model doesn't apply well to modern boat tail designs.

Because of this, manufacturers have to decide what BC to use. Some use the highest BC the bullet is likely to achieve. And, some are more conservative and use an average of the expected velocities to get their BC.
Without knowing what velocity is used to calculate the listed BC from any given company, comparing G1 BCs of different bullets really doesn't do much good unless they're significantly different (like a .273 vs a .426).

Most precision bullet makers will also list the G7 BCs for their bullets. The G7 model is much better suited to modern boat tail bullet designs, and allows for more precise ballistics calculations. But... G7 BCs are much lower for any given bullet, than the same bullet's G1 BC. So, "main stream" manufacturers are hesitant to start listing G7 BCs for their bullets. They don't want people getting confused and thinking the lower G7 BC is representative of the older standard of the G1 BCs.
Here's an article, if you want more information. (It also has representations of the G1 and G7 standard projectiles.)

October 30, 2012, 01:50 AM	#21
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	In your photo, I don't see anything truly key-holing, but they may be yawing (still a stability issue). Don't worry about the ballistic coefficients. They have far more to do with a bullet's flight characteristics, than stability. And, a bullet's shape affects the BC more than length alone. Unrelated to the OP, but related to your last post.... Note how Sierra quotes multiple BCs for their bullets. That's because G1 ballistic coefficients actually change significantly in flight (as velocity changes). And, the standard G1 model doesn't apply well to modern boat tail designs. Because of this, manufacturers have to decide what BC to use. Some use the highest BC the bullet is likely to achieve. And, some are more conservative and use an average of the expected velocities to get their BC. Without knowing what velocity is used to calculate the listed BC from any given company, comparing G1 BCs of different bullets really doesn't do much good unless they're significantly different (like a .273 vs a .426). Most precision bullet makers will also list the G7 BCs for their bullets. The G7 model is much better suited to modern boat tail bullet designs, and allows for more precise ballistics calculations. But... G7 BCs are much lower for any given bullet, than the same bullet's G1 BC. So, "main stream" manufacturers are hesitant to start listing G7 BCs for their bullets. They don't want people getting confused and thinking the lower G7 BC is representative of the older standard of the G1 BCs. Here's an article, if you want more information. (It also has representations of the G1 and G7 standard projectiles.) __________________ Don't even try it. It's even worse than the internet would lead you to believe.