Use your lungs to rapidly fire darts from Nerf magazines using this breech fed blowgun, or adapt the mechanism to your own homemade blaster. The pump grip can be cycled repeatedly to load multiple darts for a shotgun effect.

This toy can fire nerf darts at higher velocities and ranges than a standard Nerf blaster. Eye protection is required to prevent serious injury.

https://www.youtube.com/watch?v=ygJhwYmyEBc

In addition to the 3d printed parts, you will need:
6.5 inches of 2" PVC Pipe
6 inches of 5/8" x 1/2" flexible vinyl Tubing
3 feet of 9/16" x 5/8" Nylon Tube (Mcmaster #8628K57)
3 feet of "thinwall" 1/2" PVC pipe, (ID should be ~0.72")
16.5" of 1/2" Nylon Rod (Mcmaster 8541K18) or similar 1/2" plastic rod
8" of "thinwall" 3/4" PVC Pipe (ID should be ~.930")
1/4" Nylon Rod (Mcmaster 8541K14) or similar 1/4" rod
1x 1/2" CPVC T
1x 1/2" CPVC Elbow
1x 2" PVC T
6-32 screws in a variety of lengths
Some duct tape
At least one Nerf magazine, preferably the 18 round mags. Raider drums won't work.

Print one of each piece except for PB4_WingGrip2a.stl -- you need two of those. The parts are in inches, so you will probably need to scale by 2540%

Deburr the parts, drill out the large (clearance) screw holes to 5/32", drill out the small (pilot) screw holes to 7/64 and tap them 6-32.

Ream the 1/2"-ish hole on the Airblock so that it's just barely big enough to slide in the 1/2" nylon rod without getting stuck, and Stockstarter just a bit more so that the nylon slides freely through the stockstarter.

You may need to tweak the model to get useable hole sizes with your printer, most 3d CAD software will open the .stp assembly I have included. The length for PB4_WingGrip2a may also need slight adjustment to grip the Nerf magazines correctly.

Use the illustrations as an assembly guide, note that the holes in the breech linkage (parts PB4_FrontGripLink and PB4_BackBreechLink) use set screws to stay fixed to the Nylon rods of the breech.

The flexible hose is attached via a CPVC elbow to the air output. It's important to have the flexible hose between your mouth and the blaster to reduce the likelihood of a mouth injury in a case where the blaster is knocked towards you. The flexibility also helps with ergonomics. If the hose doesn't stay snug in the CPVC elbow, duct tape over it all to hold it in and improve the seal.

The magazine squeezer (the almost elliptical part) will need clearance holes to be drilled matching the holes on the wing grips. There is no pilot, you have to measure and match up the holes by hand.

The out stop is held to the barrel with duct tape, and the front grip tube is held to the front grip link with duct tape.

Insert magazines with the breech in the back / retracted position, release magazines from same position by squeezing the ellipsoid at the small ends.

Fire by blowing into the flexible tube with the breech in the forward position after having drawn it back and forth once. You can shotgun load and fire multiple darts by repeating the motion multiple times between firing.