Tunneling

The tunneling weapon fusion transforms a heavy weapon into a tool that can carve tunnels into stone. As a full action, you can fire a tunneling weapon at a wall made of unworked stone or softer materials, blasting open a space 10 feet tall, 10 feet wide, and a number of feet deep equal to half the weapon’s range or range increment; if the wall is made of harder material, this has no effect. This requires the expenditure of ammunition equal to triple the weapon’s normal usage, and you must be within the first range increment of the tunneling weapon from the wall to use the weapon in this way. The blast leaves behind rubble in all squares of the newly created space, which is difficult terrain.

Any creature in the way of this blast must attempt a DC 15 Reflex save. On a failure, that creature takes half the weapon’s normal damage. This applies no other effects from the weapon other than damage.

This weapon fusion can be installed only in heavy weapons that deal kinetic or energy damage.