Checked baggage must have TSA locks or TSA will cut/break any other lock off. This also includes any container that is inside your baggage -- TSA locks only.
Your firearms need to be in a hard case that is lockable and locked. DO NOT use TSA locks on guncases.
I guess I'll go with 60 rounds...30 rounds in each bag
Also be aware that your ammunition must be the original boxes (which can be the plastic boxes like MTM makes). Ammo cannot be loose in a bag or in belt carriers.