So why has the 6.5-ounce 2.5x Leupold M8 that's been on Phil Shoemaker's relatively lightweight .458 Winchester Magnum managed to retain zero for decades now?
Mass and inertia. The lighter scope has less mass on all if its internal components, therefore they "move" easier with the recoil vs. a heavier object that wants to resist initial movement and flexes/bends until it is forced to move.
Think about it in terms of bridge building. A super strong, totally immovable bridge due to its massive weight and strength will not handle sharp repeated shocks as it doesn't have any "give" in the system. Eventually something will get overstressed and fail. A more pliable bridge will flex, twist and adjust to the myriad of forces applied to it, without breaking.
