Caliber
The diameter of a gun's shell in millimetres, which sets what armor it can overmatch as well as roughly how hard it hits.
Also known as calibre, shell caliber, gun caliber.
Caliber is a physical property with a mechanical consequence. A shell whose caliber is more than three times the thickness of the plate it hits ignores the angle of that plate entirely, which is the overmatch rule and the reason large-caliber guns punch through sloped roofs and thin sides that smaller guns bounce off.
It also drives the shell's high explosive potential, since a bigger shell carries more filler, and it correlates with alpha without determining it.
Related terms
OvermatchThe rule that a shell with a caliber at least three times a plate's thickness cannot ricochet off it, no matter the angle.Alpha damageThe damage a single penetrating shell deals, before the plus or minus 25 percent the game rolls on every shot.High explosiveA shell that explodes on contact, dealing reduced damage through armor it cannot penetrate and splashing everything nearby.PenetrationHow much armor a shell can defeat, in millimetres, rolled plus or minus 25 percent on every shot and compared against the effective thickness it hits.