"bullet casings deal damage"
Hot casing is an upgrade that makes all the bullet casings get thrown away whenever the player shoots his gunboots, causing a small amount of damage to enemies they hit.
Casings are ejected randomly to the left or right, thus allowing the player to do damage laterally.
This upgrade's efficiency will be most effective with burst, machine gun and noppy, launching one bullet casing per charge and least effective with the shotgun, launching one casing per five charges.
Hot casing's in-game description is "bullet casings deal damage"