I checked with Delta. They have a pretty reasonable policy. I' ve included a copy. To my surprise, ammo can be checked.

Shooting Equipment
One item of shooting equipment is accepted as part of a customer' s free checked baggage allowance. For each item listed, one item of shooting equipment is defined as one or a combination of the following:

Rifles
One rifle case containing:
two or fewer rifles (with or without scopes)
one shooting mat
one small pistol tool kit
noise suppressers
11 lbs. of ammunition
Cases containing more than two rifles will be assessed an excess baggage charge

Shotguns
two shotguns
two shotgun cases
11 lbs. Of ammunition
Cases containing more than two shotguns will be assessed an excess baggage charge

Pistols
One pistol case containing:
two pistols
pistol telescopes
noise suppressers
a small pistol tool case
11 lbs. Of ammunition
Cases containing more than two pistols will be assessed an excess baggage charge

When checking a firearm, you must:
declare to the Delta representative that they are checking a firearm (If a Security Checkpoint is prior to the Delta ticket counter, you must declare the existence of a firearm to security personnel.)
present firearm(s) unloaded and sign a " Firearms Unloaded" declaration
lock the firearm(s) in a hard-sided, crush-proof container and retain the key or combination
maintain entry permits in your possession for the country or countries of destination or transit
ensure small arms ammunition is packed in the manufacturer' s original package or securely packed in fiber, wood or metal boxes
Note: Firearms transported to the United Kingdom as checked baggage require a permit from the United Kingdom. The passenger must contact the United Kingdom for more information regarding this permit.

Ammunition in excess of 11 lbs. per passenger or that contains incendiary projectiles is prohibited.