In the course of running my business I've shipped tens of thousands of packages via UPS. Descriptions should be "misc. hardware" or "machine tool parts." Pack everything yourself, print the label at home, drop it off. Contrary to what you might have heard, they don't scan or x-ray packages to find guns or gun-shaped objects. Obey state and federal laws and don't be loud and proud about shipping gun parts, and there is literally jack schitt they can do (or will do). You wouldn't tell a stranger that you have expensive gun parts in your glovebox--why would you tell them when you have them in a shipping box?