Factorio Forums

A projectile given a collision mask (such as "layer-13") and a collision box will collide with other entities (such as a "small-spitter") even though the entities don't collide with the projectile's layer.

The easiest way to replicate is to use the walls-block-splitters mod: https://mods.factorio.com/mod/walls-blo ... /downloads
and get a spitter to shoot at you over another spitter, but the middle spitter gets hit.

On ProjectilePrototype, you need to set hit_collision_mask. collision_mask is probably ignored completely on projectiles