Step 1: Gun

If u don't already have it buy the nerf gun retaltiator

Step 2: Barrel

Find a plastic tube if some sort

Step 3: Done

All you have to do is tape the tube to the gun
<p>this is very stupid, considering what JackDC2000 said and that you're just taping the tube to the gun.</p>
This is interesting, except putting a barrel on a nerf gun actually reduces range. Plus, it has no orange tip, which is dangerous because it can be mistaken as a real gun.