Disclaimer: I did not design this. Will, a commentator on my blog ( makerblock.com/2011/03/can-we-make-a-printed-nerf-dart-shooter/#comments ) , left a link to this page ( nerfhaven.com/forums/index.php?showtopic=20819 ) at Nerfhaven.com where a member named SorrowX uploaded pictures, design files, and STL's for his rapid prototyped Nerf Blaster. I've uploaded the STL's here. I suspect these parts will be way oversized to allow printing on a MakerBot. However, I'm hopeful others can build on SorrowX's excellent work.