A little hard to explain so I tried to make a picture describing it the best I could. Basically your gun lags behind where you're pointing as you turn.
Personally I hate how they increased the recoil so much on machine guns, especially horizontally. Realistically the issue with machine guns is not their recoil, but their weight and bulkiness, which makes them too awkward to room clear with. I think this solution does the best job at mimicking their weight, and would really discourage people from wanting to use one in tight areas. On top of this I believe machine guns should have much more sway and a longer ADS time.
I also think it's worth considering implementing this for all guns to varying degrees, with pistols, submachine guns, and carbines being the most responsive. It could add another dynamic to balance out different guns, since there isn't really that much difference between an M4 and Mk 18 in this. However, I do understand that this could make the game frustrating and feel very unresponsive in general, so I do want to be cautious with considering this.