From FEE:

These laws were put into place to hinder black people from using arms to rise up and break the shackles of slavery. But throughout the history of American chattel slavery, black heroes did use guns to free themselves and others. The most notable example of this was Harriet Tubman, who carried a pistol on her missions to free slaves as well as a sharp-shooting rifle during the Civil War. Mary Fields (better known as Stagecoach Mary) was a former slave and one of the first two black women to serve as a “star route” mail carrier. She famously used two guns to defend herself and the mail from thieves along her route.