OP..caution....call or visit your UPS HUB first!
I don't know where in the country you are, but be sure to personally check with your closest UPS Customer Service Center. These are known as HUB's. You cannot ship ammo from any of the third party franchise points (local drop off stores, etc.).
UPS (for me at least) recommended that I start an account on-line and then call for a residential shipment pickup, after declaring (in the on-line process) that I am shipping "Limited Quantity" which I have just (yesterday) been advised that in approx. 30 days, will become known as "Dangerous Goods".
There is no more ORM-D category, hasn't been for a couple years. The small arms ammo category is Limited Quantity and the appropriate black & white diamond sticker is shown below. Again, the blue ORM-D sticker is obsolete.
Definitely read the rules on UPS website, NO loose or bulk ammo, sturdy boxes with individual partitions (like factory boxes) then packed in outer box so that nothing rattles. Be prepared to pay extra charges for home pickup, and home delivery if you are shipping to anyone at their home. Be also prepared to NOT ship to California for ammo.
Federal Express has basically the same rules as UPS. No ammo goes by air, has to be ground.
Again I really advise checking personally with your closest UPS HUB as even if your local HUB allows access, not all employees even know or recognize their own company rules, so you still may be refused, unless you do it all from your home, with your on-line account, print your own labels, apply your own LQ stickers, package properly and then schedule a home pickup.
The above info is current for my area as of yesterday, because I just sold 6 boxes of 30-06 factory ammo (120 rds) to another Forum Member and his payment arrived yesterday. I boxed everything up, got my shipping label (No Air, ASR (Adult Signature Required, Tracking no.) printed on my home printer, applied two (2) Limited Quantity stickers, and scheduled a pick up for tomorrow. I did use Fed-Ex for this shipment, as they were a little cheaper than UPS.
Also another latest wrinkle is that advise your buyer that not only will the delivering driver have you sign for package, they now scan your buyers' drivers license or other government issued photo id. I don't know if this requirement is just Fed-Ex or includes UPS too.
The one advantage to having an on-line account is that you can know your shipping costs in advance if your buyer will PM you the delivery address. Otherwise you have to "guestimate" an amount to add in your sale listing.
As Roy always says: "Hopes this helps"