Regulating ammunition will fail Thomas' test requirements, from simple history.
The concept of Militia Service required possession of both arms and ammunition.
Further there was a burden upon the State to have ample supplies of power and shot to supply the militia, at least through 1903 & the Militia Act.
Simply stated, the Right to bear a thing implies the right to be able to use that thing.
This will find historical basis going a long way back, as there were no ordinances on carrying of swords, knives and daggers, if they were blunted.
But, bringing this sort of logic before logical entities like Courts takes time, endless amounts of time, and the lawmakers are prefectly willing to bury us is more absurd regulations.