This is my fourth attempt at a fixed magazine for short dart nerf blasters, but my first attempt that I recommend trying for yourself without massively editing first.
Not anymore---Try version 0.7 or 0.8 for best results.
Dart output is a 5/8" socket. Recommended material is a loose fit for the darts, I prefer .625" x .527" aluminum.
Fits 1/2" rods or tubes for the pusher, but the hole needs to be reamed to size. I use a 0.501" reamer followed by a 0.510" reamer.
There is a bit of support material modeled in--The 1mm walls in the gap are meant to be removed. So I recommend using a material that you can work on afterwards, so that they can be removed effectively, or you edit the CAD file to do something more clever than I did.
I used neodymium 12x3mm disc magnets for the door return. You can try anything you want, but the holes are modelled 13mm in diameter, so it has to fit in there. There is no door swing limiter, which is a pretty big omission, but it can be kludged on later relatively easily.
Mine isn't attached to a blaster yet, but it works OK despite a very sad ABS story on the front. Unlike previous versions, this has a bolt pattern for mounting to a plate or whatever, so you don't NEED to use a mountain of hot glue. It's still an option if that's how you roll.
While this should work more or less as-is, the step file is provided so you can edit to taste.
I have a video primarily about version 0.6, but it does also feature the 0.4 and 0.5 briefly to explain why they are worse than the later versions.