I've put about 7 hours into MP today, trying every weapon except the LMGs. Here's a little guide for those who haven't looked into weapon stats or haven't spent much time finding out what Assault Rifle suits their playstyle best, or what attachments suit each gun well. I will rank the guns best-to-worst:
1. SWAT 556:
A 3-round burst, but when put into full-auto, it becomes the best assault rifle in the game. Great damage/range (long 3-shot kill range, 4-shot maximum). Moderate-high fire rate(720 rpm), moderate recoil. Recommended attachments: Select Fire + Foregrip. Do not use with: Extended Mags (only 9 bullet increase).
2. Type 25:
Similar to the FAMAS in the original Black Ops, although slightly slower and less damaging. Also behaves like MW3 FAD. Recoil is low, almost too low. High rate of fire (900 rpm), low damage (4-5 shots), average range. Recommended attachments: Fast Mags + Stock + Laser sight. Do not use with: Select Fire
3. FAL DSW:
Like the SWAT 556, this gun becomes a monster when put into full-auto. Easy recoil, 2 shot kill in close range (3 at mid-long), 25 round mag. Beast weapon. Recommended attachments: Select Fire + Target Finder + Extended Mags. Do not use with: Silencer
Shoots 4 rounds within each burst. Each burst is a fast 900 rpm, and the delay time between bursts is relatively short, making a highly-mobile burst weapon. Switch into full-auto and it performs similar to the Type 25 but with slightly more damage (3 shot kill in short range, up to 5 at long range). Recoil is very controllable. Recommended attachments: Select Fire + foregrip + extended mags. Do not use with: Silencer
Like the game says, it's the most versatile overall assault rifle. Moderate damage (3-5 shots), moderate range, moderate recoil, moderate fire rate (720 rpm). Great for new players. Recommended attachments: Stock + foregrip + Laser sight (makes a very mobile setup). Do not use with: Select Fire
When in full-auto, this weapon is just a sleeper. When in burst mode, it becomes a whole different beast. When shooting this gun, the first 2 bullets always shoot twice as fast as the rest of your shots (600 rpm). Switching into 2-burst mode ensures you are pumping out bullets as fast as possible, with precision. Above-average damage and range (3-5 shots), moderate recoil. Recommended attachments: Select Fire + MMS + FMJ. Do not use this weapon in full-auto.
We're now getting into the weaker side of the class. The SMR is a lot like the FAL DSW, just with a considerably longer 2-shot kill range. However, it has a smaller mag, more recoil, less mobility, and less bullet-penetration power. Be aware that in semi-automatic, you can reach a higher rate of fire than in full-auto with a trained trigger finger. Recommended Attachments: Silencer + Target Finder/Hybrid Optic. Do not use with: foregrip
This weapon handles somewhat like the ACR in MW2, althought not as accurate. It is essentially a Type 25 that shoots slower and has a little bit less recoil. While the recoil is the lowest in the Assault Rifle class, the low damage (4-5 shots) and medium fire rate (720 rpm) may not be enough to keep up. It does, however, posess the fastest reload in the class. Pick attachments that play to the weapon's strengths. Recommended Attachments: Hybrid Optic + Foregrip + Fast Mags. Do not use with: Laser Sight or Select Fire
Handles similarly to the MW2 SCAR-H. Among fully-automatics, it has the longest 3-shot kill range in the class, as well as the longest 4-shot kill range. However, a full-auto SWAT 556 does the same thing - just better, and at even longer ranges. Unfortunately, the damage will also eventually drop off to a 5-shot kill, and combined with the slow fire rate (600 rpm) and bumpy recoil, this gun will really struggle to compete with other Assault Rifles at the longest ranges. Avoid this gun unless you want style points. Recommended Attachments: Silencer + Target Finder + Foregrip. Do not use with: Laser Sight or Select Fire
Hope this helped, other classes coming soon!