Estimating Bullet Length

[Towhead]

I've recently come across a few ways of mathematically deducing G7 and G1 ballistics coefficients, given sectional density and form factor. I've tried it out on several bullets that have info available and it seems to work fairly well. My question is whether there is a simple way to estimate bullet length, especially if you have another bullet of known length to compare it to with a similar form factor.

Here are the relevant equations:

G7 BC = Sectional Density / G7 Form Factor
G1 BC = G7 BC * 1.95

If your bullet has a G7 but no form factor information, like Hornady bullets, then you can use the same equation rearranged to find the form factor.

G7 Form Factor = Sectional Density / G7 BC

If your bullet only has a G1 BC, like Sierra bullets, then you can use the same equations again to find G7 BC and G7 Form Factor:

G7 BC = G1 BC / 1.95
G7 Form Factor = Sectional Density / G7 BC

And of course Sectional Density is only the weight of your bullet (in lb) divided by the square of the bullet diameter.

It seems like with all this information (caliber, sectional density, form factor, etc), we should be able to estimate bullet length, but I have had no success in my attempts.

I'm sure the equations for G7 and G1 BCs is not 100% accurate, but it looks close enough to land you on paper and then you can adjust from there. Does anybody have any experience with these equations?

 

[_Windrider_]

Why estimate? The actual length is available from the manufacturer.

 

[_Windrider_]

Or buy some reloading manuals

 

[Towhead]

Why estimate? The actual length is available from the manufacturer.

Just for fun. Playing in GRT with a wildcat cartridge in a .296 caliber. Trying to extrapolate what sort of max BC bullets could be available for it (Hornady A-Tip, Berger EOL, Sierra MatchKing, etc), and what their lengths and weights might be.