A breif run down of the best guns since the weapon changes in the Close Quarters June DLC/patch. These are the most rounded and useful weapons. Just a short post for those wanting a recap.
Best Assault Gun
The best class specific weapon is still the M16A3. The second best weapon is the AEK-971. It has been this way with since release really, with the AEK being slightly best post CQ due to a foregrip buff. Some players think the M16A3 is overpowered; my thoughts on the matter here.
I prefer the AEK but the M16 is more reliable and easier to use. The M16 is the best because you can spray at medium range for kills. Recoil is primarily vertical and easily controlled by counteracting using your mouse. Spread is not over the top and still decent when emptying a clip in a single burst from close to medium. At longer ranges it maintains its accuracy and has a decent rate of fire that allows it to hold its own against the big close range guns; AEK-971, F2000 and FAMAS. Reload is nice and fast, especially when not empty. The M16 is generally run with a heavy barrel and red dot scope. For attachment reasoning see this post. For sight reasoning see this post. If you wanted to run something different the M416 is the an almost exact replica, with slightly lower rate of fire.
The AEK-971 is a close second and slightly harder to use. You need to burst with it at medium range (full auto is fine in close) due to its somewhat stronger recoil and spread. It will easily eat M16 users at close range but take care at medium as requires a little discipline to not go full auto here. If you choose the AEK as your best gun you should run heavy barrel and foregrip. It is the only assault rifle worth using with a foregrip currenty.
Best Engineer Gun
The best engineer weapon is the M4A1. For similar reasons as the M16A3.
Best Recon Gun
Probably the M417. Beasty.
Best Support Gun
From the LMGs you don’t have much to pick from. Take a PDR or shotgun.
The P90 with laser is epic for hip firing. The AS VAL is good if you want to play recon or support with an assault rifle style weapon.
The best shotgun is the SPAS-12 with slugs. The second best is the MCS-870. The SPAS is better because it has a slightly higher rate of fire. Since the CQ patch you have been able to one hit kill to around 40m with both weapons using slug ammo. Pretty sweet.