-// unit: qJ / qu^3 (energy needed per volume unit of solid to push/burn away
-// parameter: bullet constant: mass / area in g/qu^2
-// = mass / (pi/4 * caliber^2)
-// with caliber in inches, mass in grams:
-// = 1.273239544735163 * mass / caliber^2
-// with caliber in inches, mass in grains:
-// = 0.082633246453312 * mass / caliber^2
-
-// bullet max travel distance inside solid:
-// 0.5 * v^2 * bulletconstant / g_ballistics_materialconstant
-
-// some bullet constants:
-// http://hypertextbook.com/facts/2000/ShantayArmstrong.shtml
-// second bullet: caliber .45, mass 16.2g, bullet constant 101.859163578813
-// third bullet: caliber .338, mass 16.2g, bullet constant 180.5476053421592
-// fourth bullet: caliber .25, mass 2.3g, bullet constant 46.85521524625399
-// http://en.wikipedia.org/wiki/.50_BMG
-// caliber .5, 360 grains, bullet constant 118.9918748927693
-// AK-47:
-// caliber .3, 62 grains, bullet constant 56.92512533450383
-// .3 winchester magnum:
-// caliber .3, 150 grains, bullet constant 137.7220774221867