bounces, despite it’s name, isn’t the right property to set. You also need to set alwaysBounceVertical and / or alwaysBounceHorizontal. From the documentation:
If this property is set to YES and bounces is YES, vertical dragging is allowed even if the content is smaller than the bounds of the scroll view. The default value is NO.
Note the confusing name in IB .. https://stackoverflow.com/a/18391029/294884