Redditor Ultimaker 2 completed a 3D printed bolt pistol from Warhammer 40K, and the finished product is impressive. You can get the model for the prop gun at My Mini Factory, from user Robert H. Abazyan. Ultimaker did a lot of cleaning to get the 3D printed gun in shape for painting. They explained:

As for the cleanup / prepwork, yes there was a ton. Printing was the easy part lol. everything had to be joined up and sanded, then bondo’d and smoothed, masked and painted. quite a bit of work. I ordered a mouse sander off of amazon so hopefully that will speed up my next build.