Re: Shooting Prone - Off hand on scope?
Whether prone or from a bench, I never rest my off hand on the scope or the stock. I still remember what my Dad taught me many years ago and can hear his voice coaching me before the shot, "Don't hang on the rifle son, that hand is for the sandbag. Relax and let go. Get Johnny (me) out of the equation as much as possible and let the rifle shoot."
I think the "jumping" of the rifle happens more so when using a bipod on a fairly solid surface. Just my experience, though. If you are experiencing this while using a bipod, some on here may can explain how they use their bipods. I think the term is called "loading" and uses the springs to keep tension on it. I own a bipod but rarely use it.
As for the hand on the scope, I don't think it will effect the scopes accuracy but rather the consistency of the rifle from shot to shot. Most modern scopes, worthy of residing on a dedicated long range rifle, are sturdy enough to withstand this pressure with no deflection of the tube. The phrase "aircraft grade aluminum" keeps coming to mind. JohnnyK.
"The only thing necessay for the triumph of evil is for good men to do nothing."