Grip the empty weapon very firmly with one hand, as if to shoot it.
Your trigger finger and thumb should play no
significant role in gripping the weapon.
With the first segment of your trigger finger
CENTERED on the trigger so as to pull
straight back, see if a pencil will fit freely between the side of the weapon and the third segment of your finger.
Then you will have a good idea if the gun fits your hand properly.
Consistency is the beginning, the middle, and the end of accuracy.