You're using lineWidth instead of barWidth. So your bars are the same width; they just look thicker (and spill over the border) because the lines around them are thick.
The reason why your bars are so narrow are because the width is expressed in axis units, not pixels. In your case, where you're using a time-mode axis, the bar width will be quite large. If you want a bar to cover one hour, then your barWidth should be 60 * 60 * 1000 = 3600000.