Modified version to able to shoot Mega dart.
I'm too lazy to get a spring, so I just modified it to be able to use a 5mm elastic string instead.
As for the plunger head, since we're not using any spring for compression, no force or pressure against it that will disconnect the head from the rod. I also disliked the original screw version of the plunger head, so I modified it. You just have to insert the plunger rod into the plunger head and superglue it.
Also included..
You will still need a few M3 screws and nuts, a 5mm elastic band, an o-ring, and lube.
For assembly, go to the origin creator page.
support the creator.
https://www.printables.com/model/242523-primus-v11-a-single-shot-nerf-homemade