Well, with me having 15,000 kills with mk46 I feel I should input.
A long time ago, I was trash with lmgs, their high recoil and spread completely putting me off using them, despite them being frankly cool looking and sounding. Over time, I learned something particular with the mk46. It has an extremely fast ads time of 133ms, which means it is easier to actually ads mid firefight than most other weapons.
The lmgs in this game have trash range, coupled with their higher than average horizontal recoil just means that at first it seemed a bit counter-intuitive to have such a fast ads, with such clear sights. However, I realised that if you could get the jump on multiple enemies, coupled with a concussion grenade , it becomes a walk in the park to just mow them down, especially with how much DPS and the mag cap. the mk46 has when shots are accurate. I find it is just better to flank with thunder and surprise a group of enemies with a concussion, which they could not predict, then mow them down with the lmgs.
But that’s my two cents, I don’t use the k121 often as I don’t like the guns really inaccurate and fires slow, same thing I feel with blish and Shar can. I drastically prefer my m62 fragger in fragment and soon to be obsidian when the season ends.