Metal supply during WWII was critically short, and almost anything 'consumable' made of metal was rationed to some degree. Examples: toothpaste (which some of us will recall came in metal tubes) - you had to turn in an empty tube to get a new one. And typewriter (remember them?) ribbons, which came on metal reels in metal containers called 'tins', same thing, had to turn in used ones to get new ones. As for ammo, I recall hearing that there were restrictions based upon 'need' as defined by Uncle Sam. As we all realize, when restrictions on availability are imposed, a black market is instantly created.
And as a side note, consider how many old 'Pennsylvania rifles' were melted down during the massive war effort drives for scrap metal.....
These were times that only our parents and grandparents actually experienced as adults, and first-hand knowledge is lacking.