One of the pre-course qualifications for the NRA Basic Pistol Instructor course is being able to shoot a 6" group (20 rounds total) on a 9" area (typically a plate) at 45ft, from an unsupported standing position using a two handed grip.
If you are able to consistently group at 4" at 45-50ft, I would consider that acceptable, even good target shooting.
There are many scenarios we can envision for self-defense shooting.
- Shooting from concealment
- Shooting on the move
- Shooting at multiple targets
- Shooting at moving targets
- Alternative shooting positions (prone, supine, seated, kneeling)
- One handed shooting
Thus, for a relatively new shooter it can be a challenge to "meter" proficiency. My goal is to build upon my most basic, fundamental shooting skills until I am solidly proficient at them, then expand into those things (and others) listed above.
I can consistently, reliably, repeatedly shoot a 2" group from 50ft with any of my factory stock handguns in calibers above .380, from an unsupported position using a two handed grip. Most instances I shoot a 1"-1.5" group.