Just finished it and have the same issue, most of the guns are pointless, as are the different ammo types. They seem to have spoiled a lot of the weapons from 3/4/5.
Once you can get an MS16L with armour piercing ammo, suppressor and 4x sight that's virtually the only weapon you need. Silent single shot kills on everyone.
On previous games it was always the .50 sniper that I aspired to, but didn't like it much this time, found the SVD a better option for those extreme range shots.
The autocrat is the only pistol I bothered with and I hardly used it. Seemed op for such an early game weapon.
Final slot RAT4 for anti-chopper duties.
Lmgs seemed pointless, not enough dmg for the kick and noise - same goes for vehicle mounted guns, they seem rubbish this time out.
Liked the shotguns, but as I play stealthy I didn't carry one often.
Didn't even try the SMGs or bows!
Whole game felt way too easy on the 'harder' skill level, with it pretty much a guarantee that I'd capture each base without even getting spotted. The 'special forces' didn't appear any more of a challenge than the normal troops, they just had a slightly different noise when I headshotted them.
Enjoyed it despite the usual FC gameplay repetition but they really need to improve NPC ai to make it more of a challenge. Oh and the pointless 3rd person sections in the camps were just weird, why did they do that?