Short Dart Mod for China Mags

Update: STEP and F3D are up. To tweak to your printer, I recommend modifying the 4 outermost guides via their extrusion depth and spacing. I'm also aware of a jam issue when the mag is fully loaded, so I updated the follower to have a taper in the offending region. Newest version is v13. This should fix the issue, I will update this when I or someone else has printed and tested it.

This design is compatible with the following China mags:
http://www.lightake.com/p/4-Pcs-Thicken-Soft-Bullet-Cl