Jerry could shoot .15 splits with a Yeetcannon - so I doubt that actual non-superhumans like me will ever get down to .12 with hits.
In my heyday, I could consistently run .15 A-zone splits with a G19, but I had regular access to a range, virtually unlimited access to training ammunition, and got sent on paid vacations to places like Midsouth twice a year. Pretty sure I couldn't pull that off now for love or money, regardless of what slick trigger I stuck in a G19. Maybe a G18 :-)