First the materials:
A bic pen
Any kind or Nerf dart
Duct tape or electrical tape
A Nerf gun
A pocket knife
First get the Nerf dart and rip off the tip, or head.
Next get the bic pen, take off it's bottom cap and pen cap and inc tube so it looks like a tube.
Next Insert the bic pen tube into the Nerf dart.
Then put some tape on the dart so the pen doesn't slide off.
Then put your modified dart contraption into your Nerf gun.
Put some tape around the dart to help it fit in the Nerf gun.
To keep the Air soft bbs from rolling out the end, use the pliers to bend the tip of the pen that is protruding from the dart so that the BB can't roll out when tilting the Nerf gun at any angle.