I went out to eat with my wife and I put on a jacket I havenāt worn in a while and I had almost an entire box of Hornady Critical Duty .45 rounds I was happy as those are around $1.25-$1.50 per round.
Wow, most I have ever found were spent cases in my pockets, you must be rich. 
Howās that for currency?
It may well be currency one day if the grid goes down or there is a zombie appocalypse, or whatever.
Itāll be more precious than gold, especially if you canāt get it. We will have to resort to slingshots with steel balls.
I was recently telling my wife that I am going to get a slingshot and start training with it.
Oh, what will the neighbors think of you then?! āI heard that Calvin is strange; I heard that he has lost his mind.ā Watch out, you may be red flagged because to your change in routine. smh. lol.
They already think I am strange, but they know that I am the guy that checks the perimeter at night, to make sure nothing is out of place or suspicious looking. 
Hmmm, Iāll bet you have a Tin Foil hat, donāt you? LOL!
I hear you; I tend to practice a little vigilance as well. Itās just my nature or evolved sense of awareness that I practice doing it. Hopefully, my wife will never be forced to understand it.
I already used it as currency during the pandemic.
A couple of guys doing some electrical work saw my reloading equipment. They wanted to know if I would sell some 9mm. Of course I canāt sell the ammo that I made, but I used some of my store bought stash to pay for the job at an exchange rate of 50 cents/round. At that time, 9mm was getting close to $1/round. Good deal all around.
I havenāt heard you say nothing about it. I donāt know nothing about nothing. 
There are a large number of writers who dabble in Apocalyptic Fiction or Scripting scenarios who agree on bullets as currency 
.
There are some high-end slingshots that are no joke. You still have to practice and learn how to use it, sure, but itās pretty scary how much force you can get from a strong sling with an arm brace. I think you could take down Goliath pretty reliably, or at least make him reconsider his life choices.
Iāve got a friend who has a high performance sling shot. At short range and " having the ability to initiate". I could see a use for it.
Oh no you didnāt say, āarm brace.ā You do know in some states having an arm brace on a slingshot is illegal. Be sure, lol, to check your statesā laws on slingshot types. lol. seriously.
I have a friend who had to explain to TSA why he had a .357 magnum round in his pants pocket
Lucky! Some states (looking at New York) would have pressed charges.
Used to call them Wrist Rockets, made with surgical tubing if I remember right.
Yes, I believe thatās correct.
Less seriously, if a slingshot has an armbrace, ATF considers it an āassault rifle.ā