This one's hard to answer exactly, without having the data to experiment with, but here are a couple of ideas ...
Perhaps you could make the entire chart taller (such as using "goptions ypixels=1000"), which would give more room for wider bars.
Perhaps try changing the device (there might be slight differences in bar spacing between dev=gif and dev=png, and there will certainly be differences with dev=actximg and dev=javaimg).
And if the values along the bottom/response axis of your hbar chart have a format applied, and if that format 'pads' on a lot of extra space on the left (such as if you're using the "comma20." format, when your numbers only need 4 or 5 digits), then you might try using a smaller format to free up some space to be used by wider bars in the bar chart.
These are just some ideas - not really sure if any of them will be your "silver bullet" though! :)
Message was edited by: Robert Allison @ SAS