HiddenPuppy

You don't actually need that much food, just visit a tavern/supermarket.. You're bound to find food of some sort

Not 100% sure, but I think that in the dayz lore, the UN or some European country came over the help, but could not stop the spread of the infection. I suppose this could mean that some m4s/USP's could be left behind (European weapons).

For the same gun to use the different bullet, you'd have to change the barrel. So it'd be like having 'm4 - 7.62' compared to 'm4- 5.56'. But yeah, an interesting concept of the same gun spawning with different calibers. (Some Glocks use .40 or .45, rather than 9mm)