A third defendant was placed on probation.
The U.S. Justice Department said Kyle C. Montgomery, 23, and James Smiley, 27, both of Chattanooga, were also ordered to serve three years of supervised release after completing their time behind bars. Colton L. Partin, 22, of Apison was sentenced to 18 months probation, including six months home confinement.
The defendants, who pleaded guilty in January, also are to perform 300 hours of community service.
Federal authorities said the trio repeatedly drove by a group of at least four blacks who were on a porch at East Lake Courts public housing in the early morning hours of July 9, yelling racial slurs and shooting fireworks at them.
While none of the targeted individuals were injured, one blast shattered an apartment window. One explosion was caught on video.
Celebrity Families of 2014 [PHOTOS]