[@Beach Burrito]

I like you, you know your boolets.

To answer your question, yes, high grade rounds would be your Federal in the pretty white box (or anything else manufactured pre-apocalypse). Dirty would be your post-apoc and pre-apoc steel case, corrosive primed, etc rounds.

And heavy rounds would indeed be something like explosives, a 40mm or pineapple grenade would go there.

EDIT: I've also posted my own CS for a rough idea of what to do if you still had questions. It still needs to be ironed out some, but for now it should hopefully suffice to answer stuff.