That is simply wonderfull, I am in love with big robots and unit that you presented of humanoid type mecha have good fighting equipment and looks like could go into battle anytime and certainly is a real deal enemy. How I wish to be a pilot of such a beauty, cause this machine gun could take down anything (I wonder how much his shield would withstand of this calliber bullets)
Well, a quick rule of thumb for ballistic armor is that the armor needs to be as thick as the round it's supposed to stop is wide. So judging by the size of that shield, I'd say something around a 5-7" cannon shell.