If you have a Stoeger 2000, you should also have Cyl, IC, Mod and XF choke tubes, unless you bought the gun used. Buy several boxes of buckshot and try it with different chokes to see which one patterns better.

Of course, I'd probably more strongly recommend that you ditch the buckshot and go with rifled slugs. They'll give you longer range and are far more lethal. Buckshot doesn't exactly have the best rep as a humane deer killer.

Mike