I see these guys have you pointed in the right direction.[&:] One thing I'll mention that no one else has. If you force your fingers straight out (open hand), you tighten the muscle in your hand just below the thumb. Try it and feel what I'm talking about. Now relax and close your hand so your index finger and thumb barely touch. Relax, relax, relax. Now feel that muscle.
Same with your release hand. Relax. Find a good repeatable anchor tight to your face. Play around with grip and anchors a bit and watch your groups move around the target.