The reason I have two guns that share ammo is something called standardization. Basically with two guns that share ammo I don't have to fumble around or worry about which ammo to buy. So no more "i need x of that and x of this." or "Oops wrong ammo," and potentially getting a jam.
So don't worry I have only one "big gun." AKM is the correct designation for the modernized AK-47. Like the AKS is the AK-74. as for side arm... forgot about that... hmm I stil need to finish it but I'll look into it. Oh and the bayonet is basicaly a knife so I think that's okay, I mean I don't need a giant sword or whatever.