The Dart Gate in my Alpha Trooper broke, so I quickly designed a replacement in FreeCAD.
So far it seems to work well enough, even though I couldn't design based on the original part, because it went missing. I basically made a brick with the bare minimum of cutouts needed for it to work.
The model might work for the Retaliator (and other Nerf products, I just happen to own a Retaliator) aswell, since the dart gates look very similar.
I printed with 100% infill in PLA. The hole for the hinge is probably not the correct size on your Printer. Although i oversized it by 0.2mm (over the 1.5mm of the pin), I needed to drill it out with a 1.5mm drill bit.
The author marked this model as their own original creation.