Try different brands of shot to see what works best,maybe try diff.chokes.
Just this season I was talking to an aquaintance and they always drive deer , he uses an extra full turkey choke 3" rem. mags 00, and made a kill at 97 yds. he didn' t think it was that far till he paced it off, but I' ve watched these guys drive , and shoot, most shots are between 10 and50 yds. if allowed in your state maye try a rifled choke tube. I just nailed one at 110 yds. Also the barrel not being fully rifled lets you shoot buckshot fairly decent up to 45 yds for those times when you can position yourself some where within a drive. you just have to keep experimenting and asking questions. Good Luck