interesting, never before heard of Munz metal, but have heard of "zinc-steel" (what the precise alloy is, I have no idea) that was used for the 1943 penny and "steel" used in EC 43 .45ACP cases. Have heard of steel .30 carbine cases, but never seen any.
Do note that the steel was only used in 1943, and in 44 the supply and war situation allowed a return to brass cases and copper pennies.
Which, btw, is one of my questions when someone touts the benefits of steel cased ammo. If it's as good as they claim, why did the US govt go back to brass in 44 when they could have stayed with steel back then?
.30-06 is kind of the "basic" case of the standard .473" head size. Its about the longest case common in that head size, so, almost any shorter case can be formed from it. I've even seen it shorted all the way to .45acp (and reamed).
Saw an article once where a guy made .30-06 into .22-250. Took several intermediate step forming dies, but it was done successfuly.
Its worth more than just scrap brass value to someone, possibly more than usual due to the current shortages, but I expect those to be only a temporary, though painfully inconvenient, thing.