The Boomco Whipblast is hands down my favourite dart blaster in terms of the mechanism. You can fire it extremely fast and even one handed. The only huge disadvantage it has, is that it is only a one shot blaster. This absolutely didn't make any sense to me, until I saw that Hasbro holds the patent for the smart-AR (air restrictor) technology, which allows firing more than one dart without needing a clip or a drum (you can find it here, should you be interested). Since Mattel holds the patent for the mechanism (you can find it here) I noticed that there will probably never be a multi shot version of the Whipblast, so I sat down and build my own.

The Nerf Whipblast is painted by Matt Bull, better known as Billy2917. If you want to see more of his awesome creations, check out his flickr profile.

Step 1: What You Need

Materials

BOOmco Whipblast (e.g. on amazon.com)
Nerf N-Strike Guardians Of The Galaxy Rocket Power Blaster (*)
Modelling clay
Sanding paper
Primer
3x M3 nuts and screws
Two component glue
Modelling clay
Optional: KS140 and KS139 brass tubes

Tools

3D Printer (not 100% necessary, but helpfull)
Optional: Drill, Dremel, saw

* Finding the blaster in the US seems to be tricky. Europeans can find it here. Please, drop me a comment should you know where to get it. With the Nerf Rebelle 4 Victory Blaster Nerf Rebelle 4 Victory Blaster, Hasbro is releasing another 4 shot smart-AR blaster, which might be a nice alternative.

Step 2: Fit the New AR System

You can of course 3D print an adapter to connect the plunger of the BOOMco Whipblast to the smart AR system, but I decided to use the front from the Rocket Raccoon blaster.

First use a saw to cut the front part from the plunger of the Rocket Raccoon blaster off, as shown in the first picture. Since the opening is slightly too small you will have to widen the hole. Then glue it to the plunger from the Whipblast as shown in the third picture.

Next you will have to cut a hole into the shell, as shown in the fourth and the fifth picture, to fit the new mechanism into the Whipblast. I suggest that you use the "case1.stl" and "case2.stl" pieces from the next step in order to know where to make the cut. I used a Dremel Speed Cutting wheel and it worked really well.

Step 3: 3D Printing Time

Start by printing all the necessary pieces. Add the nut to the newly printed shell piece.

As you can see I designed the new front of the gun as multiple parts, the reason for this is that I wanted to reduce the number of needed support structures. So you will have to glue the pieces in place, as shown in the second picture. Don't forget to glue the nut into the "front1.stl" piece.

Glue another nut to the inside of the holder piece and attach it to shell of the Whipblast as shown in the third picture.

Drill a small hole into the middle of the orange piece that holds the barrels in place, so that it can be screwed to the "front1.stl" piece.

Use glue and expoxy putty to glue the new shell pieces in place. As you can see in the pictures I also removed the "wings" from the whiplast and filled the holes with the "circle.stl" piece.

Step 4: Replace the Barrels

This step is optional, but I suggest doing it. Else the darts might fall out, when you smash the gun down.

Be very careful that when you cut the barrels off that you don't damage the air restrictors. I used a piece of tape to mark an even spacing, as shown in the first picture.

Now cut four about three cm long pieces from the KS139 tube and press them into the plastic barrels (it requires some force). Then cut four pieces from the KS140 tubing and slide them over the KS139 tubes. Before you glue everything in place, make sure that the "front1.stl" piece (from the last step) still fits.