If I read the OP's first post right, 20 rounds averaging 2", 7 yards, in ~20 seconds is shooting very well.
There's nothing to see here. Time to move on.
If someone wants to tighten the group even further, slow down for awhile; keep practicing; pick-up one's speed later &/or increase the distance.
Choose one handgun and don't be looking for a hardware "cure" right now.
I mean striving to be better is a good goal, but it sounds as if the 180 point score on a 3" diameter over 20 rounds at a fast pace is already a good score for that drill. Look at it another way; that's 18 rounds all in 1", with two flyers.
Everyone misses. That wasn't the point. They were catastrophic misses. Not even in the same zip code. Of a category I didn't see with other calibers and I wasn't really getting what I felt was helpful advice from local instructors.
I'll be honest I think most of my normal shooting issues (vertical stringing enlarging groups) is caused by visual acuity (sight alignment variation due to clarity). My groups are usually twice as tall as wide. I guess it's time to see if the optometrist can manage to help me with that. I think the real fix is that fountain DeSoto was looking for.