Generally, we would encourage you to use the new RadChartView
control over the former RadChart
Controlling the bar segment width in a RadCartesianChart
has been discussed in the following thread
For your convenience, I'm attaching a sample project as a demonstration.
Additionally, I suggest you go over the available demos in the WPF Controls Samples
and SDK Samples Browser
to get a good idea of how to use the RadChartView
Please inform me whether the approach suggested by my colleagues in the forum thread works for you. If you need any further assistance, please let me know.