kyler, check to make sure that the pellets are not clipping the baffles on the shroud. A good way to check for this issue is to coat the baffles and end cap of the shroud with liquid white out (used as correction liquid when using a pen when writing). It is non-permanent and can easily be removed. If clipping is not an issue, and you have ruled out everything else, it might be your shooting technique. I am highly doubtful the problem is your scope as even a self-repaired objective lens on a Leapers scope was able to withstand my springer.
DO NOT EVER TEST FOR ACCURACY USING A VISE! This will only make you chase POI forever. A gun - even a PCP - needs to recoil and vibrate in the manner it chooses to. A vise will only prevent it from doing so. In most cases, a vise will transfer the vibration it receives from the rifle during recoil back to the gun before the end of the shot cycle.
I know it's a hard pill to swallow, but in order for a shooter to shoot with precision, the gun has to be "one" with him/her; that means the shooter must move with the gun together (from the gun's recoil), unless he/she is able to find a way to let the rifle shoot to the intended point-of-aim by itself. Upon recoil, the gun must not move in one direction and the shooter in another. This is why I choose not to shoot bench-rest style because I am much more able to consistently manage my rifle's movement. I am also more accurate this way. To shoot accurately via bench-rest is to make sure that you have everything set up precisely so that the rifle's firing cycle is consistent all the time. Personally, I am able to sense, or feel, rather, whether my rifle is held incorrectly when I am shooting without a rest.