I see people attaching bubble levels and whatnot on there guns and scopes trying to get perfect level. How would you know your gun is even level? Since most guns aren't flat on top how would attaching a level on the barrel you know its even level. So when I install my scope. I hold the gun to where it looks straight and level for my eye. Then I loosen the scope rings and rotate the scope till the cross hair is level. I double check that gun is still level and cross hair is also level using only my eyes. No bubble level or any attachment. Am I doing it right or am I doing it the wrong way. When I go to my crosshair is level, that's all that matter or is there more to it than just having crosshair level during shooting.