Derp I misunderstood those settings, I thought they affected only new games. Thanks jodokus31.
Practically, I can't disable Realistic Weapons because it deletes all the ammunition without replacement.
However I can workaround by decreasing turret range bonus.

Turning off K2SO's "Realistic weapons" setting ensures that all shots fired can hit their targets, fixing this issue.

I still think this outcome shouldn't be possible, but maybe it's not an engine 'issue' then?
Unfortunately for me, the settings in these two mods are Startup settings, so I guess ...

It seems the combination of "Krastorio 2 Spaced Out" and "HeroTurrets_Redux" creates turrets with weird range issues.
For context, as turrets kill more enemies they 'rank up' and get increased range.

I created a reproducing save with a gun turret firing at a worm in a particular position, which it ...