A guy here made these needle dart things out of magazine pages, which he then put in the back of tagger darts. He is getting 120+ feet with his blowgun now.
So he basically filled in the hole at the back of the dart, making it more efficient to fire.
Results from modifying dart lengths depend on the gun, though it won't always work. For example, the Air Zone suction-head darts are shorten than their Nerf counterparts, and they CAN be fired out of a Maverick. They usually just flop out of the gun though.