So, as(I guess) all of you know, when you reload, the cartridges in your magazine are simply added to the ammo count, so if you shoot 3 bullets and there are 6 cartridges left on your ammo reserve, you will have full 10 cartridges on your magazine, with 3 remaining cartridges. My suggestion is that we implement a real magazine system, so you will spawn with, lets say, 1 magazine in your SMG and 4 others in the ammo reserve, if you shoot 8 bullets with the SMG, when you reload that magazine with 22 remaining cartrides is going to be a separate magazine.
It is kinda hard to explain, but imagine this:
There is, instead of a ammo count showing all your remaining cartridges, 1 bigger number, representing the next magazine if you reload, and 3 smaller numbers, representing the other magazines. By pressing F, below R, it will cycle to the next magazine, so you will reload the biggest magazine avaliable. Like this:
--22
--30
--14---<------Those are magazines avaliable
30---<------This is the magazine you will use if you press R
This would make people think about their ammo reserve and plan better which magazine to use, as you may want a magazine with a smaller ammo count if there is only one enemy left, but a full mag if there are more around. Also, would add a small touch of realism, that is not present in any game that I know of.
PS: Oh, and it would only be used with the Semi Rifle and the SMG, as the Shotgun reloads individual shells.