He wouldn't have any regulatory issues selling ammo to me in PA, he could just ship it UPS or other marked ORMD.
States like NJ, IL, CA, and some others have myriad regulations about this, and rather than research them, I'd just avoid them entirely. Mail order ammunition is completely prohibited in Chicago, for example, must be purchased at a retail store. I can have a case of ammo dumped on my front porch. Cook county collects a 5 cents per round tax on ammo sales. I think CA (and probably other states) have ID or documentation requirements for sale and purchase of ammo.
I'd stick with well-known gun friendly states, and avoid any you even think might be problematic. I refer to states like IL, CA, NJ and others with unreasonable regulation as commie states.
I still think his best bet is to find some buddies who might like to shoot the ammo and work a F2F deal with them locally.