As sp6x6 noted, ammo is separate from the rifle on air travel, likewise, the possibility of a no show for both rifle and ammo is always there.
Since your concern is the ammo, why not just send extra ammo days ahead to a designated pick up point (friend, family, outfitter, etc ...).
In the mid 1990s while stationed at Davis-Monthan AFB, my friends and I hunted elk in the Hannagan Meadow area in AZ. One of my hunting buddy only had 6 140gr .270 rounds due to last minute sight in adjustment and ran out of time to pick an ammo before our travel. He was hoping to pick up ammo at the Hannagan Meadow area. Plenty of places to purchase but all sold out. Luckily, he didn't need it.
We all have back up rifles with plenty of ammo except him.
I voted for my "FREEDOM", "GUNS", and "MONEY" - keep the change - UNK.
"I am always proud of my country!"
"Leadership Rule #2: Don't be an @zzhole." - Maj Gen Burton Field.