I DL'd the original file here but it was terrible and every piece needed to be re-modeled. I did the chore and this is the result. I've printed two now successfully. There are 52 pieces in all, grouped into 13 prints. This is intended as a static display model. It does not shoot anything. The only functionality is the bolt and spring do cycle and the clip is removable. I have plans to modify further so collapsible stock can open, but right now you have to choose when building it open or closed stock. I will add close up pics of finished model after I airbrush it.
In light of the comments left I have added the sliced .x3g files. They are for my dual extruder so some mods may be needed for your setup.
Recommended print settings (std. or Fine at your discretion.)
Print Group A: with supports 100% fill
Print Group B: 30% fill min.
Print Group C: with supports min. 30% fill
Print Group D: 3 shells with or without supports
Print Group E: no supports 30% fill min.
Print Group F: with supports 100% fill
Print Group G: no supports 30% fill .1mm layer
Print Group H: no supports 30%+ fill
Print Group I: with supports 30%+ fill
Print Group J: with supports 30%+ fill
Print Group K: 100% fill
Rail: with supports 50% fill
Tube: no supports 3 shells 30%+ fill