I've got an M60 class I like to use. Got Flak, Hardened, and Hacker Pro (until I can get Gas Mask Pro). I keep a motion sensor on me and either patrol a small area or try to follow my team for some heavy back-up.
The HK21 is like a hybrid between the M60 and Stoner 63: good RoF and AR-like enough to save you if you end up in a one-on-one battle, but the RoF is still slow enough for sustained fire. You need to move from place to place depending on the spawns and how the enemy is approaching, and make sure to take out their chopper support and CS planes so they have to come to your spawn area. Don't waste rockets on the spy planes because they already know you're guarding the flag where you spawn.
psn: seven62mil if I get killed by it it's OP, and if it's OP it's noobish, and everyone who uses it is a camper
The problem with smoke grenades is that you almost always need to have a flack jacket with you, lest the defender sends a rocket towards the flag. But even then you cannot guarantee there won't be a LMG user who will proceed to empty his mag at your direction.
If you insist try the nova gas one.
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