There's 10 different ways you can ship it. If you have an account with UPS already, then generate the label yourself with all the specifics and amount you want to insure the "replacement value" of the contents. Deliver it directly to the UPS driver or UPS hub.
UPS Stores will not take a firearm generally, and if it's over $1K, then you will want to deliver it to the driver.
FedEx makes you over night a firearm, which is 2x to 3x more cost than needed. UPS can go ground, 2nd day, or over night. Lots of choices and easiest to work with, by far when it comes to ammo and firearms.
UPS driver at your door step, vs going to USPS and waiting in line at USPS. I'll take UPS. USPS sucks for deliveries, also, at least on my end.