With r2 I found that I killed more with the marksmen but grabbed the carbine to replace my magnum wen possible.
If ur chimera the plasma secondry fire is the best killer in the game! Target a cluster of enemies e.g skirimsh wen they have nearly taken a node and kamikaze into them and when close enuf deternate. I wud rack up 5-10 kills depending on match in that one moment and they wouldn't have a clue what hit them.