There is also an issue having to deal with mass-weight-inertia. A large, heavier objective bell is more succeptable to breaking off under the recoil generated by a big bore. A gun builder friend of mine had 2 consecutive large objective, expensive European scopes have the objective bell snap off while sighting in his 416 Remington. The scopes were covered by warranty, but that does little good when Mbogo is bearing down on you and your scope is in two pieces.