Calling the Chicago Bears an offensive juggernaut might seem to defy logic, tradition and the lineage of gritty defenders from Butkus to Singletary to Urlacher. Believe it. Getting a huge boost from their trademark defense, the Bears scored the first five times they had the ball Sunday and ruined the homecoming of former coach Dick Jauron with a 40-7 drubbing of Jauron's Buffalo Bills to go 5-0 for the first time in 20 years.