I also used M240, MG4, L-whatever(the first one) and AUG. They were all alright, but RPD, even with the slower fire rate, I just seemed to do best with. Two pro's I think are the large magazine + dead-on accuracy.
L86 LSW is what you were looking for. I have a whole bunch of kills with the L86. The L86 has the third highest fire rate of the LMGs; unlike the M240 and MG4, the L86 has the same high damage of the RPD. In medium range encounters where burst firing the weapon is easy to control, the L86 tears through people. Long range encounters are hit or miss with the L86 though. The biggest benefit to using the L86 over the RPD is reloading; the L86 is fed by a drum magazine, as opposed to belt feed of the RPD, and takes half as long to reload compared to the RPD.
The L86 with its higher fire rate is pretty good but I like to use it with a sight which leaves me without a grip unless I use bling but that means I can't use OMA.
At first, I did not like the iron sights on the L86, but I have grown accustomed to the lack of any real features. I typically pair the L86 up with Sleight of Hand Pro; the combination of faster reloads and faster aim down sights is invaluable, especially since LMGs have a longer reload and aim down sight times. If I manage to run through 200 bullets on the L86 and thus need something like One Man Army, then I am on a pretty serious tear, have probably killed quite a few people, and most of the other team likely has a very good idea where I am located and is searching me out for revenge.
The MG4 is pretty good but it has the same issues for me as the L86 plus it has the lowest damage of all LMGs in the game.
I have barely used the MG4, but apparently the iron sights are misaligned on the weapon, basically making some sort of added sight mandatory. The misalignment of the iron sights partially explains why I found the weapon to be less than ideal for its intended purpose. I may need to try the weapon again with a Red Dot or Holographic Sight.
I've never actually used the M240 online. Its one of the few weapons I can't comment about.
I tried the M240 out the other day when we all played together. The M240 has basically the same iron sights as the M16A4 and I do not like the iron sights on the M16A4. If either the front sight were less obstructive or the rear sight ring were larger, then either set of iron sights would be more bearable. I have the same issue with ACR's front sights; the front post is much too cluttered. With all of that said, I may give the M240 another go and unlock the Red Dot Sight. The weapon has very little recoil without a Grip attached and having a better sight picture with the Red Dot Sight may be all I need to be effective with the weapon.
RPD is one of the most accurate guns I have. I have outsniped the snipers with that gun, countless times. The gun is useless without the grip.
I do not know about accurate, but with the grip attached, the RPD has a very consistent recoil pattern. The RPD is a dog without the grip though.
I don't think even the AK74 in black ops is nearly as good as the UMP in MW2.
Personally though I always found it almost worthless without rapid fire.
I am back and forth on the UMP45. I feel most comfortable with the UMP45 with either a Red Dot or Holographic Sight attached, but typically I am most effective with the weapon suppressed. For the most part, SMGs are just not really in my wheel house in MW2. My best games with SMGs have properly come when paired up with Marathon, Lightweight, and Ninja or Commando and a Tactical Knife USP45, which is a game play style I am not overly comfortable using.
