How to Make a Nerf Gun

Choose your ammunition. Nerf guns launch darts primarily from spring energy, but it is also possible to launch them with pressurized air. In order to make this work properly, however, you have to customize the size of your launcher to the ammunition you will be using. For example, if you are using ½-inch darts, use a tube with an inside diameter of ½ inch..

Use two PVC tubes, one slightly smaller in diameter than the other, to make the launch chamber. The smaller tube should fit inside the larger one. The length of the tubes is up to you, but for smaller darts, you'll probably need less length, typically 12 to 18 inches.

Place the smaller tube inside the other so that the smaller tube sticks out about 2 inches. Tape the smaller tube to the larger tube so that it remains still while you drill it.

Drill a hole near the end of the large tube where the smaller tube is sticking out, drilling through the top of both tubes. Remove the tape and pull the smaller tube out about half of its length. Drill another hole through the smaller tube (but not the larger), ensuring that the two holes in the smaller tube are aligned.

Use the utility knife to cut the smaller tube between the two holes, leaving a slot as wide as the drilled holes. File off the rough edges. This will be the guide track for your inner tube. If you have difficulty cutting the slot, you may want to drill occasional holes to break the job down into portions, or you can use a jigsaw if you place the PVC tube in a vise.

Place two or more layers of duct tape on the end of the small tube farthest from the holes you drilled. Fit the smaller tube into the larger tube, adding more tape wrapped around the edge of the smaller tube as necessary to get a snug (not tight) fit; you should be able to move it back and forth with only a little effort. If it drags when moving, use a little 3-in-1 oil or WD-40 to provide lubrication.

Thread the screw through the outside (larger) tube so that it passes through the slot of the smaller tube. Attach the nut, but do not tighten all the way (the washer should be located near the head of the screw to prevent it from being pulled in).

Load the tube. Test fire the tube to ensure that you're getting enough air pressure. Pull the smaller tube back and push forward quickly; this should launch your dart across the room nicely. If you are not getting any distance, you may have a leak and will need to add more tape. If you are getting adequate air, add a drop of superglue to the nut on the screw to keep it from coming loose and falling off at a critical time.