May i recommend you buy a 5 gallon bucket of spent 9mm brass? Add another 5 gallon of 223/556, and etc etc. Buy as many as you are willing to store. I have held brass for a very long time.I'm looking to open a position in gold/silver. What is the most cost effective way to purchase physical metals?
Spent cases are 70% brass and 30% nickel in material. They store easy, takes very little space (stack them) and store very long time, and comes in very useful during ammo shortages as everyone move towards reloading. And if you need extra weight to hold down say a tow behind aerator...it works excellent every year.