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Old 04-01-2017, 06:36 PM   #7
Join Date: Aug 2004
Location: Buffalo, New York
Default Re: GURPS ULTRATECH ballistics?

Ok, so I decided to try an analyze the different approaches to damage values, muzzle velocity, Joules per gram of a given substance etc - all the while using both GUNS, GUNS, GUNS by Greg Porter and the spreadsheet that you devised, along with the formulas for what I used in order to that I could use specific real world data of bullet weight in Grains and bullet velocity in feet per second (how the data is displayed in CARTRIDGES OF THE WORLD 8th edition - I know it is at a higher edition than 8th as of today!).

So, here's what I did. I used both of Greg's formulas - Muzzle Velocity and Muzzle Energy, to double check against each other, and the original real values for any given bullet (the one I listed earlier with a bullet mass of 130 grains and a bullet velocity of 1180 feet per second).

Using your formula given on your spreadsheet, the Muzzle Energy for a 130 grain bullet travelling 1180 feet per second works out to 544.8475086 Joules. Greg Porter's formula gives a value of 541.9681402 Joules.

Using only Greg's formula for Muzzle Velocity (I didn't try to reverse engineer your formula, but I'd imagine if I did reverse engineer your formula, it would be slightly different than Greg's formula)...

(544.8475086/8.4238583)^.5 x 44.84 = 360.6181343 Meters per second or 1183.1304 Feet per second.

Using Greg's calculation formula for Joules in the equation:

(541.9681402/8.4238583)^.5 x 44.84 = 1180

So, it isn't surprising that using only Greg's formulas for Muzzle Velocity and Muzzle Energy will be internally self-consistent in order to double check things.

Your formula for Joules is:

.5 * Weight in grams/1000 * (Velocity in meters/sec divided by 1000)^2

I'm guessing that you were trying to use the formula such that it used unit measures of Kg and Kilometers

That's my guess overall.
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