Abstract: A practice tear gas round comprises a projectile having the same caliber as the standard tear gas gun, and a main adapter which is separately loadable into the launcher and has an outside diameter of the same caliber as the launcher while providing a chamber of reduced diameter for use of the launcher with devices of smaller caliber than the launcher. Preferably, an auxiliary adapter is receivable within the chamber of the main adapter in order to further reduce the caliber of propelling charge which is to be used for the practice round, while allowing removal of the auxiliary adaptor in order to receive in the main adaptor a standard 12 gauge shot shell, for example, for use of the launcher as a single shot 12 gauge shot gun. Additionally, the standard gas gun can be converted to a single shot rifle or shot gun for firing various other smaller calibers of cartridges and/or shot shells according to the auxiliary adaptor selected and inserted into the main adaptor for reception of a cartridge or shot shell.