As explained and summarily down-thumbed in the entry for 120
(don't you love the editorial power of inifinite monkeys?), "120" is a numerical acronym symbolizing religion, with specific reference to peace of mind acquired through respect of a diety but conspicuously without awknowledgement of any particular sect.
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.