Actually you can use other than hub for shipping, just depends on the store's policy. Our local independent place accepts ammo and firearms. I've used them several times and they've never even batted an eye, even got a roll of ORM-D stickers by the scale.
Whether or not some small stores will ship ammo or not I don't know. But I do know for a fact that it is a blatant violation of UPS policy to do so. It's a line I'd prefer not to cross. UPS has a rather strict policy that only permits 2 ways of shipping ammo. #1 You are on a regular UPS route and your stop is a regularly scheduled stop (AKA, the UPS man drops by every day to check to see if you have any packages to ship that day). or #2 You take it to the actual UPS service counter/location which is often at the hub.
Can you ship outside of those 2? I guess if you can find a place that is willing to violate UPS policy then sure.
I take all of mine to the UPS hub on Zionsville Road in Indy. The guy there (Mike I think is his name) is a "gun/prepper" guy and great to work with and is there in the late afternoon/early evenings. He did tell me the last time I was in shipping a rifle to make damn sure I never shipped any ammo in with a gun. Obviously shipping both separate is fine with proper markings on ammo box. However, both in the same box is a big no-no. He said they had a customer that shipped a shotgun and even though they asked him if he had any ammo in the box he claimed he didn't but really did. Somehow ATF found out and he was arrested and is facing some jail time.