Inconsistent Firearm Stats

[Varyon]

I'll post it when I get home (if I don't forget), but IIRC Doug's spreadsheet largely boils down to one equation, something like ((Kinetic Energy)^1.03)/(Cross Sectional Area), multiplied by a constant, to get average damage (divide by 3.5 to get damage in dice).

[DouglasCole]

Originally Posted by Varyon

I'll post it when I get home (if I don't forget), but IIRC Doug's spreadsheet largely boils down to one equation, something like ((Kinetic Energy)^1.03)/(Cross Sectional Area), multiplied by a constant, to get average damage (divide by 3.5 to get damage in dice).

I actually had cause to revisit this a bit for simplicity and some degree of accuracy fixes this past December, which was the first tweak I'd done to it since 2013.

Points of Damage = sqrt (KE in Joules/ (Caliber in mm)^0.4) * 0.6

Nice easy numbers relative to the prior ones. It's an empirical fit, not a physics fit, so don't look for deeper meaning here.

Bit better fidelity with GURPS published values for many common rifle bullets (which tend to do pretty well for real-world benchmarks).

[Varyon]

Originally Posted by DouglasCole

I actually had cause to revisit this a bit for simplicity and some degree of accuracy fixes this past December, which was the first tweak I'd done to it since 2013.

Points of Damage = sqrt (KE in Joules/ (Caliber in mm)^0.4) * 0.6

Nice easy numbers relative to the prior ones. It's an empirical fit, not a physics fit, so don't look for deeper meaning here.

Bit better fidelity with GURPS published values for many common rifle bullets (which tend to do pretty well for real-world benchmarks).

Nice. Yeah, certainly liking that simplification.

[hal]

Originally Posted by DouglasCole

I actually had cause to revisit this a bit for simplicity and some degree of accuracy fixes this past December, which was the first tweak I'd done to it since 2013.

Points of Damage = sqrt (KE in Joules/ (Caliber in mm)^0.4) * 0.6

Nice easy numbers relative to the prior ones. It's an empirical fit, not a physics fit, so don't look for deeper meaning here.

Bit better fidelity with GURPS published values for many common rifle bullets (which tend to do pretty well for real-world benchmarks).

Now for the fun part...

I tried using that formula listed above, and using the iconic 7.62mm NATO round. It ends up giving me a 7d6-1 result compared to the original formulagiving 7d6+0. That Variables I used was

Bullet Mass 150 Grains, Velocity 2800 ft/second, diamater 7.62mm (used Cartridges of the World for this one. Wikipedia uses a 147 grain bullet in its entry for 2800 fps. The three grain difference made no overall difference in the value of damage for 7d6+0.

This It was easy to insert a new line into my spreadsheet and call it "new Damage" using your new formula. I already had a kinetic energy entry on the sheet, so for the variables above, I got a KE value of 3539.77 Joules.

IF it helps, my formula for Kinetic Energy was:

=(BulletMassInGrams*VelocityInMetersPerSecond^2)/2000

The spreadsheet contains a new damage value listed as:

=((KineticEnergyInJoules/ProjDiaInMM^0.4)^0.5)*0.6

Results under the original formula were 25.1 for average damage under the old method, and 23.8 points with the new formula.



Not sure if this helps or not.

[maximara]

Originally Posted by kenclary

It should be added to the unofficial FAQ thread.

I added it and related material here to the GURPSwiki.