And if that ain't right, then show me straight to the judge
Just like Bryan Nichols I ain't spittin', nothin' but slugs

from B.o.B (Ft. T.I.) – Im Dat Nigga Lyrics on Rap Genius

Meaning

Bryan Nichols is well known for his killing spree in Atlanta, Georgia in 2005. B.o.B is also from Atlanta Georgia! In his killing spree the first person he killed was the judge who was going to sentence him to jail time. Likewise, B.o.B is going to murder(lyrically hopefully) whoever disproves of his music

Also, important to note is the fact that nickels are often pounded with a hammer to flatten them to the size and shape of a quarter in order to fool vending and toll machines. The resulting misshapen coin, or any metal formed as a counterfeit coin, is called a slug; so the nickel/slug wordplay makes this a double entendre.

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