Today’s invention is an alternative use for an assault rifle-type weapon.
Load the firearm’s magazine with blanks (especially powerful blanks might be a good idea). Then slip onto the shoulder pad one of a range of impact tools…such as an axe head, a spade or a stone chisel. These would come with thumbscrew clamps to fit any rifle (together with various additional external handles, similarly attached).
Press the tool against a tree or a wall and pull the trigger. The automatic-fire recoil would be strong enough to act as an effective tree feller or rock drill etc -useful for building rather than as a way to kill people.