USPS won't do it. UPS doesn't let private shippers make hazmat shipments, AFAIK, so that would leave you looking for a shipper licensed for hazmat shipping to do it for you, but who would likely want to be paid for the trouble. A much easier route is to have the nephew drive up for a visit (so he pays for the transportation) or to prime his cases for him and send those. Primed cases, like live ammo, do not require hazmat fees. What I don't know is if UPS requires you to separate each case in its own sleeve or ammo box hole, as they do with live ammo. I know UPS does not allow you to use their drop boxes or a UPS Store to ship live ammo, so it's either scheduled for a pickup, or you go to a UPS hub that has counter service. Their website has these details. Maybe it will also discuss primers somewhere, but live ammo was all I looked at last time around.