In regards to your question about an adjustable objective. What this feature one a rifle scope will do is allow you to be more accurate by eliminating parallax at a specific distance say 100 yards for example by allowing you to properly focus the scope. Parallax being the effect of the crosshairs moving in relation to movement of your head. So say you move your head/eye right the cross hairs will move left in relation to the target causing you to adjust your aim to the right more, changing your point of impact on paper. If you have a scope with an adjustable objective, you can adjust it for the range you're shooting at to eliminate this so that the cross hairs will stay stationary even with slight movements in your head/eye position. As well there are also scopes that come with what is called a side focus, which does exactly the same thing, focus the optics to eliminate or minimize parallax.


















































