Ah, I see. So then why has the conserving of casings never even been considered on this show at all? I mean... I had actually wondered about that a number of times before, but now it seems overwhelmingly obvious
No need to conserve the casings if you've no means to make a new bullet and presumably no one in The Group, or of any of the groups we've ran into, has the knowledge or resources to do it. The ingredients for gunpowder are very simple and easy to acquire but it's not enough you have to have the right "recipe" to mix them in the right quantities to make the powder useful. Get the recipe wrong and the powder will either just burn rather than explode, smolder, or do nothing.
The metal to make the bullet would be fairly easy to come by, you could use pretty much any metal you come across, old coins, tin cans, hell even collect spent bullets and melt them down.
You need the resources to generate a strong enough fire to melt down your metals, fuel is probably becoming more and more scarce.
You need the equipment to to collect the melted metal and to transfer it into the molds.
You need molds.
You need the materials and equipment and devices to properly measure out the right amount of powder, pour into the casing and then to press the bullet into the casing and seal it.
And on top of all of that you need to get/make the primer. (When you pull the trigger on a gun it retracts the firing pin, when the gun fires the pin snaps forward, strikes the primer, the primer ignites the powder which expels the bullet from the casing.) Either Eugene knows how to make the primer as well as the bullet or he's found some unused ones in a factory.
Pressing the bullet into the casing is a fairly delicate and obviously dangerous process. There's tools/equipment to do this at home, but I don't suspect in this world it'd be easy to come by.
Moreover you need
time to do all of this, and when you're constantly on the run from murderous people, monsters, and rarely stay in the same place very long and have to find more immediate things (like food) there's little chance to do this. Now that they're "settled" somewhere and have divided up their human resources for scavenging or creating food and for taking care of the wlakers, Eugene has a chance to put together how to make bullets and find a place and equipment to do it.
Making the bullets is in theory "simple" but there's a lot to do beyond "just doing it." It's not something anyone has ever considered as being possible or practical but Eugene, as evidenced by the hair, obviously thinks outside the box. He may be a bit of a doofus and lied about the "cure" thing but he has shown himself to be quite smart so he was able to put this together.
And as smart as all of our other characters may be, they're likely not "science minded" or broad-minded enough like Eugene to contemplate a plan like this until now it's probably been easier to just find bullets than to make try and figure out how to make them.
