PROJ DECAL
PROJ_DECAL is a defineprojectile property used to set the tilenum of any decal spawned by the projectile, i.e. bullet holes.
Syntax is:
defineprojectile <tile number> PROJ_DECAL <number>
Where <number> is the tilenum of the decal used. Only works with bullet projectiles.
Doesn't work with bullet type projectiles fired by actors other than players.