A death grip on the ball is never a good thing. It causes all sorts of problems. The primary cause of a death grip is the feeling you are going to loose the ball. If this is the case, it is probably not drilled corectly for you. I suggest you find a good pro shop and have the ball fited to your hand.
You want a completely free arm swing. Any tension at all either in the hand or arm will cause you to "muscle" the ball. This is counterproductive to a good clean release.
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