this.
The 'Build and break' drill is phenomenal at exposing bad positioning. Combine it with a dot drill and you've got a good recipe for getting better very fastly. I also doesn't expend too much ammo. Maybe 20 rounds or so, especially if you dry fire your ass off after you build and before you squeeze the round off.
stand up. Get one round. Build your shooting position. Dry fire a crap ton, making sure your reticle doesn't move at all when you dry fire. After 27 perfect dry fires, shoot the one round. Repeat this process 10-20 times.