UPS, not so good IMO. Ship USPS. No problems there. And as far as 'what's in the box' questions, firearms of any type are subject to theft. I would never say that a gun is being shipped. (Not saying you should violate any law), but if your actions are legal, why reveal to a stranger that a weapon is being shipped? The 'machine parts' reply is perfect. It is the truth, and keeps the nature of the contents of the package safe. Just my .02.
NRA Life Member