One thing I noticed is you are loading the file "wcrate1.3ds" four times. Each of your debris entities a2 through a4, you can just use copyentity instead of loadentity and all of a's properties will be copied as well. All you will have to do is place the new entity.
EDIT: Another thing I just noticed is you have your bullet's entityradius set to 0. You should set it to .1 because that's what your bullets are scaled to. A radius of 0 is of course, nothing, and that equals no collisions.
a=LoadMesh("wcrate1.3ds") ScaleMesh a,1,1,-1 FlipMesh a FitMesh a,5,5,-5,5,5,5 PositionEntity a,300,-2,-30 EntityShininess a,-10 EntityType a,SCENE RotateEntity a, -5,8,0 a2 = copyentity(a) PositionEntity a2,280,-5,-30 a3 = copyentity(a) PositionEntity a3,270,0,-20 a4 = copyentity(a) PositionEntity a4,250,-6,-10
EDIT: Another thing I just noticed is you have your bullet's entityradius set to 0. You should set it to .1 because that's what your bullets are scaled to. A radius of 0 is of course, nothing, and that equals no collisions.