hittite said:
I'm not sure about the others, but the AK was named after its inventor Anton Kalashnikov.
Incorrect. The name stands for "Kalashnikov automatic rifle, model of 1947" or "Автомат Калашникова 47" in russian and the guy who made them is is called Mikhail.
Back on topic: some things you shouldn't do:
-Take an existing gun and increase the number behind it to make a better version, it just looks stupid when you're talking about an M16A7E2 or an MP199.
-Don't be anal about everything following exactly the same naming convention. No two manufacturers or nations can agree about it in reality.
-Don't add famous historic guns too far into the future. P90's look cool and will be around for quite some time if nothing unusual happens but using them in 2200 is like running around with a musket today.
-Nobody nicknames their guns "The Exterminator".