Apparently, the default behavior for an XY bar graph is to vary the width of the bar depending on how much room each point has in the X direction. It's possible that there's a way to override this, but I can't see a way to force the bars to be fixed-width.
I modified this example [link removed; example no longer available] to accomplish what you want, though the underlying data had to be expanded in order to do so. The attached library has a top-level example VI that shows how the process works on one of your datasets. You can modify your code to use my example by using two of the "XY Data to Fixed-Width Bar Graph" VIs to operate on your datasets.
Hope it helps,
John
