If you like to run 5.56 guns, you may run into shortages. So here is how you can find more:
Look for loose 5.56 magazines in the world, in shelves or on tables. They usually are filled with random amounts of bullets. (Magazines in containers tend to not spawn as many, or any bullets inside of them).
And now with the ammo shortages, finding a 30-mag with 23 5.56 FMJ rounds is an exciting item to find. Because that is a wad of cash worth 10k roubles.
Then you can use that ammo yourself, sell it to a player, and buy much cheaper ammo for other weaker guns in larger quantities.
This is the beautiful thing about a find-only barter economy, the game does not box everyone into the best ammo. The shortages promote diverse gameplay and reward smart choices.
That 23 FMJ rounds could sell for 10k, and then one could buy 200 9×19 PSO rounds. Not the most powerful ammo, but depending on your shooting accuracy and ammo conservation, you just bought yourself enough MP5 ammo to survive 5 raids. Or your could invest that 10k into 5-10 mosin rounds and make sure these shots hit.
Or you specialize in being an ammo supply runner. You seek out ammo spawns and then offer them for a fee on the market to others.
This entire gameplay layer is only possible because of the find-only economy. Who needs a kiba key to get excited when finding a 30 box of AKM PS feels like hitting a treasure box?