So looking at machine guns, in a light role context. I stand by the C6 as a objective thrasher, especially with SF kit and C2 sight.
Its the manning that becomes important. I believe the C6 MUST be manned properly. Hell in my experiences, even if your sections are down to 4-5 guys, just get the damn G-pig manned properly.
I have to admit, I have used the C9 alot in my career. Its volume of fire is impressive at section level, but it does have limitations. I never liked it when some damn idiot thought 1 should be carried on recce patrols.
The KAC LAMG sure looks cool. When thinking about employment of LMG/LAMG weapons, looking at the platoon in a hasty attack or deliberate attack context. The GPMG (or pair of them) is destroying the target. The LMGs are used for security/cut off and can be brought to bear on consolidation (for quick reaction to counter attack). I really like the idea of guys assaulting trenches/bunkers/vehicles during an ambush/building armed with carbines and pistols, NO LMG right intimately on the assault. I also like the idea of DMR with 7.62mm or whatever crazy caliber KevinB says works. DMR can pick out key targets, observe target for fire effects and have them paired up with LMGs on cut off/security (scopes for observation and keep re-enforcing enemy at range with accurate fire)