CrashFu, if they wanted LMGs to be different but not superior to assault/battle rifles, there are plenty of ways.
-One perked gun. LMGs are considerably heavier, so they would take up most of the inventory, whereas you can carry two rifles.
-Speed. You can run a lot faster while pointing a rifle and carrying another than you can while pointing an LMG.
-Sight stability. Lifting a LMG to your shoulder while standing, you can't keep it steady nearly as easy as a rifle.
-Dissuade headshots. It's safe to assume that KF2 will have superior hit detection than KF1.
In KF1, hitting the air to the sides and even above a zed's head wasn't a headshot, but it was a hit. If that won't be the case anymore, then headshots will be much more of a risk/reward choice. LMGs would only have to be moderately inaccurate in order for headshot attempts to much more impractical than for rifles. Alternatively to inaccuracy, you could brute force it by giving the LMGs lesser or even no bonus damage for headshots.
-Minimum burst length. You can't tap out single shots, maybe not even double taps. In Black Mesa they used this mechanic, and although it's obviously unrealistic, it was a fantastic gameplay mechanic to balance it out so that you wouldn't forget about your pistol, which could use the same ammo and efficiently fire one round at a time.
-Penetration preferred over damage. Rifles tend to get loaded with ammo that yaws, fragments, or expands, which tears up flesh better. LMGs tend to get loaded with ammo that will poke straight through instead, for the sake of barrier penetration. So the LMGs could do less damage than a caliber-respective rifle, but they could also hit multiple zeds. Maybe penetrate walls and such too, if the engine would support that kind of thing.
Also, one thing to consider, they said each perk has four distinctly tiered weapons, and maybe some side grades.
What if TWI was pulling a red herring by showing us four rifles? By caliber, we can safely assume the SCAR is a tier above the assault rifles, and the 9mm AR15 is obviously the bottom tier. But the AK12 and SA80 might be on the same tier. That would leave a tier unaccounted for, so maybe LMGs are Commando's tier 4.
Vi-PE, no, no fifty caliber machine guns, even mounted. You are massively underestimating the weight and power involved.
A deployable mounted gun of a lesser caliber could be great, though.
Probably standard rifle caliber eg 7.62x51, but you could go a little stronger with a 338 magnum or some such.
Or go weak and fast with a 5.56 microgun.
