What is 120's?
As explained and summarily down-thumbed in the entry for
120's, therefore, are any quantity of religious nouns, and are highly contextual. The term is commonly used to reference religious lessons, religions texts and spiritual moments. Furthermore, among faiths which engage in ritualistic cannibus consumption as a means of altering perception, 120's may refer to marijuana cigarettes.
It has nothing to do with guns.
From a sketch on disc 2 of "Wu-Tang Forever:"
"Yo, I'm studying 120's right now. Call me back at the god hour."