An elastic rubber band launching toy gun that uses a new method to launches 24 elastic bands in rapid succession using a simple assembly of only 13 individual parts, and featuring an optional, adjustable, sliding shoulder support stock. It is designed to resemble a Heckler & Koch MP5 firearm, as manufactured by Heckler & Koch GmbH of Oberndorf am Neckar, Germany. The rubber band gun includes a slideable, lockable stock which can be slid and locked into multiple lengths away from the butt of the firearm.

An illuminator accessory exchange structure includes an illuminator body arranged on a toy gun, a first connecting portion arranged on the illuminator body, a sleeve element sleeved outside of the illuminator body, a second connecting portion arranged on the sleeve element, a shaping portion arranged on an outer surface of the sleeve element, a front cover element arranged on a front end of the illuminator body and the sleeve element, and a first and a second coupling portion respectively corresponding to and connecting with the first and second connecting portions. By means of the arrangement of the first and second coupling portions and the first and second connecting portions, the front cover element is used to fix the sleeve element on the outside of the illuminator body, and the arrangement eases replacing of the sleeve element, in order to exchange for a sleeve element having a different shaping portion.