The term is often used disparagingly to emphasize the poor quality of the gun, or for political reasons to emphasize easy availability (gun control). The term is meant to evoke the image of a bar fight (which are most common on Saturday nights).
Currently, most so-called Saturday-night specials are manufactured by a group of handgun manufacturers located in the Los Angeles area, known as the ring of fire manufacturers.
The term Saturday Night Special originates from early twentieth century term "Nigger-town Saturday Night" according to Bruce-Briggs.