Thanks all for the information. I did not know it was possible to zoom as a gunner. This made it possible for me to complete the single mission with three Abrams tank. I was playing as commander before and it was the commanders equipment that I was curious about (my initial question was fuzzy). In this picture of an M1A2 you can see a "periscope" of some sorts on the right side (I have assumed that is for targeting with magnification, correct?). As ArmA has the A1 model that feature is naturally not available (M1A1).
So, regarding the M1A1 - does the commander have access to magnification of some sorts (in real life)?