An in-line clip is a great way to have multiple shots for any nerf gun with a PVC coupler. This is an extremely simple process which produces great results.

Step 1: Gather Your Materials

materials
4 inch piece of CPVC
4 inch piece of PVC (make sure the CPVC can fit inside the PVC snugly. if it does not easily fit in, sand down the outside)

tools
Dremel with sanding bit ( you can also use a drill with a dowel wrapped in sand paper to make a make-shift sanding bit.

also
a Nerf gun with a PVC coupler

Step 2: Sand Out CPVC

take your sanding bit and run it along the inside edge of one end of the CPVC (picture 1). continue this until there is a wider inner diameter than before and there are no burrs (picture 2).

Step 3: Put the Two Pieces Together and Fire

Take your PVC and CPVC and insert the CPVC into the PVC with the sanded out part facing into the PVC. Now your pretty much done. Load 3 stefans into the PVC part and make sure that the first dart partially enters the CPVC. Insert into the PVC coupler of your gun of choice and fire. Then prime the gun and fire again and the second dart will fire. Same with the third dart.

Step 4: How an Inline Clip Works

An inline clip is kid of like an RSCB clip but its IN-LINE (wow). When the baster is fired, the air goes through the PVC and around the dart because theres room around the dart and then the air pushes the dart out the barrel like a regular barrel. While the first dart is being fired, the next dart is carried into the barrel so it can be shot the next time the gun is fired.
If is not a good explanation, please ask me to edit this and make it better.