LMGs are pretty horrible, if you ask me!
The Ameli has too much recoil. Chain SAW can be beat at even close range (and I refuse to play sneaky with an LMG). The LSAT is okay, it is just a rip-off assault rifle that moves slower but nonetheless manageable. (I miss it when it was in Bo2 )
M27 is probably the only good LMG. It handles great, reloads fast (by LMG standards), and kills just as fast if not faster than an Assault Rifle.