I missed this somehow, so my apologies.
I live in South Africa. You can download the regulations from the websites; but I guess a lot of it is a moot point now given how travel restrictions work. Despite what it has said on the sites in the past they have pretty much insisted on a lockable separate (i.e. not in the gun case) container. I also use a small Pelican case, but thy are heavy. You can also use a petty cash tin, or I've even used and old MTM pistol case with the lining torn out (very light). The weight cannot exceed 5kg for the ammo. One worthwhile trick is to weigh it without the padlocks in place and to put them on at the gun check counter.