The TTK in this game is approx 3-5 (2-3 with headshots) and revolves around strong upper chest, neck and head accuracy. I get that.
My biggest issue with the shotties and k121 is that they have a TTK of 1-3 with BODY SHOTS, which require much less accuracy on a much larger hitbox.
Yes the k121 takes a while to reload but it has 50+ rounds… yes the shotguns have low clip size but I still feel they are too powerful. Increase K121 recoil and spread, reduce shotgun damage per pellet
TLDR: shotguns and k121 let people have a headshot ttk while merely aiming for bodies