Sectional Density and BC mathmatics...

[Melt215]

So, I'm trying to wrap my head around finding data that I need to develop drop charts for my 223 and 308. I've found that the equations are simple and straight forward but there are different approaches to find sectional density.

Some equations use bullet weight and bullet diameter and others use bullet weight and caliber to find the sectional density.

And with todays ammo, is it best to use the G7 form factor to find BC such as 168 Federal Gold SMK BTHP.

Any help would be appreciated.

 

[Heavy barrel]

JBM will do all the work for you.
http://www.jbmballistics.com/ballistics/calculators/calculators.shtml

 

[chevytruck_83]

Bryan litz's book applied ballistics for long range shooting will also tell you everything u need to know.

 

[CatShooter]

Bore diameter is more accurate.

Caliber is often not accurate - ie 38 caliber is really .357 diameter. 270 is almost .28 (.277).

So bullet diameter is the way to go - but the SD is not extremely critical.

 

[Lapua40X]

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Some equations use bullet weight and bullet diameter and others use bullet weight and caliber to find the sectional density.
...

How about running the same data through both programs and see how their outcomes compare? It is sometimes possible to approach a math problem from different directions and still arrive at a satisfactory conclusion.