Hi Lenoj,
According to your description, you want to decrease space between columns in a stacked column chart, right?
In Reporting Services, there is a property called PointWidth which can get or set the relative width of data points. The default value of this property is 0.8. In your scenario, to decrease the width between columns, you can increase the value of this property
(like 0.9). When the column width increase, the space between columns will be decreased accordingly. But please note, if the value is greater than 1, the columns will overlap. For more information, please refer to this article:
SSRS and Microsoft Chart Control How To: Change the Width of Bars and Columns.
If you have any question, please feel free to ask.
Best regards,
Qiuyun Yu