You can tighten patterns by using larger pellets, harder pellets, buffers, lower velocities, and different burn rates; or combinations of the above. May require experimentation.
Federal claims in their advertising for the Black Cloud steel loads that their FliteControl wad tightens patterns. This from the PatternMaster web site:
The second part of Black Cloud’s secret is their unique and patented FLITECONTROL™ wad. Its rear-braking technology works opposite a standard wad—staying with the shot charge longer for tighter patterns. It also gets to the target quicker and with more overall energy.
