The RGB6 is a 40mm, 6-round Croatian grenade launcher introduced in 1996, copied from the MGL Milkhor grenade launchers.
They were based on the MGL in South Africa due to gaining a contract from the manufacturers of the MGL. After gaining the contract, they also set up production facilities to implement the weapons, resulting in their being mainstream in the Croatian forces by the 2000s. The RGB6 possessed a spring-driven revolver-type cylinder for handling six grenades. Because of this, it delivers grenades with greater accuracy than simply being thrown, and is capable of taking out even enemies with body armor or enemies hiding behind objects. However, users will need to fire the grenade at a specific angle because the fired grenades travel on a parabolic trajectory.
A RGB6 made its way onto the Big Shell during the Big Shell Incident in 2009 which ended up procured by Raiden. In addition, it was also Raiden's first time using the weapon, period, due to it never being utilized in VR training.
Behind the scenes
The RGB6 was a procurable weapon in Metal Gear Solid 2: Sons of Liberty.
The RGB6 also appeared in Super Smash Bros. Brawl as Solid Snake's grenade launcher as part of his Final Smash. Although the weapon itself doesn't reappear in Super Smash Bros. for the 3DS and Wii U due to Solid Snake himself and, by extension, his final smash not returning, it is given a slight reference with Zero Suit Samus's final smash, called Gunship, where the player aims the Gunship's turrets at the players from a first person view in a similar manner to Snake's firing of the RGB6 via the drop ladder of the Kasatka in the final smash.