I actually imagine that this is more or less exactly what we’re supposed to assume is happening when we find ammo.
It’s basically something like the flour/powder thing - we have to assume that the flour for example is in a bag when we take it out of its box - why else would it not mix with other powders when you put it into the same place, making it inedible in the process?
The same probably goes for ammo. we usually find ammo in groups, for example 50 shot of 9mm ammo ; we just have to assume that those 50 rounds of ammo are in a box.
Making something like the Go-Bag for ammo would just be tedious for the player ; you wouldn’t be able to access ammo anymore when it’s basically hidden inside another item, you would have to literally dissassemble the item first to get to the ammo - something that consumes time and is no fun. If you read my posts, you know I’m all for realism, but this isn’t working out in the long run.
What would work out is a small container - a box obviously - which can be filled with (any) rounds of ammo, like a magazine for example. However, the ammo must still be accessible for reloading real magazines or guns, without unecessary unloading/dissassembling. Not sure if you can reload magazines with bullets from other magazines, if you can, great, if not…well, that would be something that needs to be added.
Of course, the Devs could possibly also just add the cardboard box as standard container for bullets, but I’d prefer a method where you can put bullets inside the box too - that won’t happen though, not as long as someone overhauls the inventory system. Sigh.