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ER-01

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**Homework Statement:**I am trying to figure out how to calculate the BC from two velocity readings with a known distance between the two readings

**Relevant Equations:**BC = (AirDensity * Distance) / ( SQRT(Velocity0) - SQRT(Velocity1))

In long range rifle shooting, knowing your true ballistics coefficient is very useful. You might get a ballistics coefficient listed on your ammunition, but depending on your range that ballistics coefficient might not be accurate. I have two velocity readings at 0 range and (let’s say) 100m. How can I calculate the ballistics coefficient for that shot?

I have been looking at this thread to solve ballistics coefficient (BC) with two velocity readings:

https://www.physicsforums.com/threa...t-bc-from-two-velocities.958802/#post-7069285

The author gives this formula to calculate BC,

BC = (AirDensity * Distance) / ( SQRT(Velocity0) - SQRT(Velocity100))

but in the variables, he provides a "air resistance" value and not "air density". I am aware these can't be used interchangeably and cannot find a clear answer on the internet.

Values given by author:

Air Resistance = 0.0052834

Distance = 100 meters

Velocity0 = 914.4 mps

Velocity100 = 838 mps @ 100 meters

BC = .451

Can someone help me out?

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