uibutton - Wrong frame values for UIButton

Question

I have a scene with a UIButton placed on it which has these parameters:
origin=(x=131, y=136) size=(width=760, height=570)

In viewDidLoad I put these coordinates into a CGRect variable:

CGRect myRect  = _mainImage.frame;

When checking myRect in Landscape orientation with NSLog I get this:
origin=(x=131, y=136) size=(width=504, height=570)

But the width value 504 is the value for Portrait orientation.
When using the same thing in Portrait orientation I´m getting the same values.

Any ideas?