There are multiple variants, such as replacer, non replacer (Standalone), and iron sight, no iron sights. The Standalone Gauss Rifle can be purchased from the Gun Runners, The Silver Rush, and lastly Knight Torres (BOS Armorer).
Installation - Use NMM, or place the contents of the archive into your data folder.
Installation - Use NMM, or place the contents of the archive into your data folder.