Cock back my tongue like a hammer, my head is like
A nickel-plated bammer, spit forty-five caliber grammar
RZA lets fly with an extended metaphor whereby his mouth is akin to a gun. A .45 handgun to be exact (one of the most powerful available). He explains that when he speaks (cocking back his tongue) words shoot out of his head as from a nickel-plated weapon. ‘Bammer’ = slang for gun.
To help improve the meaning of these lyrics, visit “Deadly Melody” by Wu-Tang Clan (Ft. Streetlife) Lyrics and leave a comment on the lyrics box