PLA(MG Chemicals) using Print-rite + Octopi. Modeled in Onshape. Link: https://goo.gl/I8JaVi The air chamber, spring and plunger is from an actual Nerf Gun and the rest is modeled and 3D printed. I learned that the foam Nerf needs a snug-fit in the barrel for best use of the air pressure. If I will redo the design I might try to make a small tube that fits snug inside the foam Nerf.