The weapons I've been using are awful at any sort of mid/long range firefights, I can't hit anything over about 300ft away, miss well over 50% of the time at the 200ft range (purely guessing the distance but still child's play for any sort of rifle) and only start to have any real effect in CQC. I always used to end up with some kind of DMR or sniper rifle by the end of the game so I decided to switch it up a bit this time and now have an M4 Carbine I got from a mod I installed (basically an assault carbine with a red dot sight).
Something that I've only really thought about recently is the effective range of most weapons (referring to guns).