I echo Wogpottor's comment about having someone insert dummy rounds randomly in the magazine (or chamber) while you're shooting live ammo. It's really the best way to detect what you might be doing wrong.
We've used that tactic when training handgun shooters and it's especially useful for the instructor to see what the trainee might be doing wrong.
People are like rifles. Some are tried and true, having great eyes, personality, and fun to be with. Others never seem to hit the mark with you. Still others go off half-cocked. Still, it's nice to know most of them.