If you dig around deeply enough in CFR 1910.120, you can find where certain quantities of ammunition are allowable for air shipment under the regs. Shippers tend to force you to ship ground (meaning they won't ship it air, not that its not legal), to avoid all possible issues and costs if they happen to violate the letter of the regs.
interestingly enough while a certain amount of loaded ammo is allowed by the regs, NO amount of blank ammo is allowed to go by air. (note, this info was accurate at one time, but may no longer be correct. They do change the regs from time to time. Always to make us safer, of course...
Ship it freight by truck, labeled per the shippers direction, you won't have any trouble, other than maybe sticker shock.