I've testing responsive in iframe, my code look like this.
<iframe src="http://revzilla.com" height="1600px" width="100%" frameborder="0" style="padding: 0; maring: 0; border: 0"></iframe>
Have you included a
viewport tag on the source of the iframe and the file itself?
<meta name="viewport" content="width=device-width, initial-scale=1">
Remember that the literal pixel width depends on the user's device pixel ratio, so if you are viewing on retina devices where the device pixel ratio is above 1 then the amount of pixels will scale with it.