14 February 2014

Coefficient

Blah!

I say again BLAH!

Ballistic coefficients are based on a bullet form factor.

The traditional form is known as the G1.

A newer form that more accurately reflects the shape of modern boat-tail bullets is G7.

In general, if you see an unlabeled BC you are looking at the G1 number.

A problem arises when the bullet maker uses what I'm going to call a G1 proxy.  The stated BC doesn't calculate to either G1 or G7 value, but if the proxy is entered into a ballistics calculator instead of G1 the trajectory matches measured empirical data.

I'm looking at YOU Barnes.

If you enter their BC number in the G1 spot in the calculator, you get an accurate trajectory that's confirmed by people actually going to the range and shooting.  It does not match the G1 as calculated and any G7 derived from thinking the published BC is the G1 is wrong.  Way wrong.

Hat-Tip to Phil for borrowing his aero-E calculus rocket-scientist brain.  When I'm a zombie, I'm eating his brain first!

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