i have a lot of fun with this:
Primary - M27-IAR with Red Dot Site, Grip, Muzzle breach (extended range and accuracy one)
secondary - so useless but the sig P226 with the silencer looks/feels sweet. i own one in real life so its even more fun
tact - FB
nade - semtex
both throwables are near useless too
perks - i play more standoff which really only works on a few maps, stalker, ghost, attachments, takedown
this way you can beast mode a heavy machine gun and no one can really get a fix on you. the mini map is so shitty.
you have to buy some of the perks becuase they dont unlock until a certain level. which is fucking forever.
also the support kill streak is the only one i use. ballistic vests, night owl, oracle/ air superioty ( jsut because if fucking love the A10 man do i wish i owned THAT)