How big is iPhone 6 screen? Cool comparison tool

You have a size wrong in the Iphone 5. You're not taking into account the width of the scroll bar (if any).

The wrapper should be 20em wide and the iframe inside should have 21.2em wide. You should also use overflow:hidden on the wrapper.

Out of all of these I've found this guy has done it the best so far and is the best representation of how a websie actually looks on an iPhone 5

http://www.nodex.co.uk/services/mobile-responsiveness-intera...

Perhaps you can look at his CSS and see how he did it?