Summary

edit: See also this later version, which is sized for 1/2" PVC and has sloped flaps for better dart stoppage .http://www.thingiverse.com/thing:431138

Soft, foamy projectiles with ~13mm caliber (this includes Nerf elites or streamlines) can be pushed through into this endcap easily and the last one forms a pneumatic seal that won't get blasted back out by low air pressure used in toys ( < 25 psi). This version is fitted for a 5/8" OD magazine.

Instructions

Print DartDoorEllipse1.stl and DartDoorEllipseCoverPlate.stl.

Use whatever infill settings you and your printer like for the DartDoorEllipse1.stl, and print DartDoorEllipseCoverPlate.stl solid.

Cut a rubber sheet per drawing DartDoorRubber.pdf.

Had a dart get blasted through with my current rubber sheet. I think 1/16" or thicker would be wise

The thickness and overall precision is not very important for the rubber sheet. I used scissors and a razor blade to make all of the cuts--I probably didn't need the razor. DO NOT use a drill to make holes in rubber sheet.

Fasten the parts together using 6-32 x 3/8" or 1/2" screws.

Put both screws through the cover plate and rubber sheet. Then drive one screw partly into one of the pilot holes in the main body. Push firmly while doing this, the screw needs to self-tap. A powered screwdriver is recommended for this. Then fasten the other screw the in the same manner, and finish by tightening both screws until the rubber sheet is gently sandwiched between the plastic parts. completely.

Push Through Endcap for Tube Magazine