I think the cross hair was visible enoug, my problem was more about visualizing the trajectory of the projectiles, and seeing them end their course. I didn't know if I needed to be spot on, or just to align my tank, my cross hair and my target so the bullet will go there. And it would help understand if you can shoot through other enemies or buildings or if you need a clear line of sight to hit your target.
I think I needed more connection between my tank and where I was shooting.