First, I would enlist a travel agent that specializes in firearms and Africa. Like
@TRAVEL EXPRESS. They know the ins and outs. PH’s are helpful but they are certainly not travel agents.
On two trips to Namibia my ammo was not checked on arrival. Just that the rifle SN# matches the Nam paperwork.
You should be more worried if you have to transit through a country that will also check your firearms and ammo, like SA. If so, just use a VIP rifle service and that basically takes the risk down to zero. When you use those services they hardly even check your gear.
I think you will be fine but DEFINITELY use a travel service to help with firearms and questions, concerns, paperwork, etc