Quote:
Originally Posted by hal
According to the book form, which states that the volumes are based on Hemisphere plus cylinder volumes - simply halving the volume of a sphere will produce a hemisphere. Knowing that the Length to diameter ratio is supposed to be 2 to 1 gives me some means for estimating the height of the bullet as being equal to Aspect ratio x Diameter minus 1/2 diameter (for the hemisphere aspect). So, the formula for the volume would simply be 4/3 * R^3 * Pi all divided by 2 (for the hemisphere) plus 1/2 Diameter * R^2 x Height for the Cylinder.
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I stole this from Doug's spreadsheet:
volume in cubic cm = (PI*(Bore/2)^3 + PI/12*Bore^2*(2*Bore*Aspect Ratio-Bore)) / 1000
where bore is bullet bore in milliimeters and aspect ratio is bullet length / bullet bore.
It doesn't match the G3G numbers, but it doesn't have any discontinuities and its's pretty close.
Bullet volume and density are very much a best guess in my opinion - it's hard to get precise data especially as you move into the past. Some things are really well documented, some things aren't, and sources don't always agree with each other. If you've got a formula that works, go with it.
You can use Vehicles 2nd ed rules to make guns for GURPS4e, if you're willing to work out how the numbers change. Personally, I found the Vehicles 2e rules to be a little vague, hence my spreadsheet upthread.