This is a modular rifle system based on the blasters for Rogue One. You can swap out the barrels and stocks to fit your configuration. You just need to use a 1in PVC pipe.
I have included the full large pieces and smaller sections for smaller printers.
Credit:
This was mostly a group effort. The base handle/receiver part started out as model I found in the SketchUp warehouse from Derik V. I modified it to be 1 solid piece and to make it work in this system. The large barrel, big stock & scope came from Coozco here. He handed them over and I modified them to work and make them a bit more accurate. The small plug and the side greebles are from Jswaggs models. I just made them to fit.