MakerBot Print is our newest print-prepration software, which supports native CAD files and STL assemblies,
allows you to interact with all your printers via the Cloud, and many other exciting new features.
This question has been asked multiple times over. As stated in several comment responses, an in-depth video and the print settings in the description and makes, use a 2-3 mm brim to catch the angular edges of the picatinny rails. In the future please take the time to look through these resources, as I have spent my time making them to avoid repeating myself on these rookie questions. Keep in mind that this applies to future prints you might encounter and is directly tied to the resolution at which you are printing the geometry vs volume of said geometry per layer.