The "Tickler" Grenade Launcher is a powerful direct fire weapon utilized by mobile frames.
|“||Many Terran Expeditionary Marines favor the GL-122 “Tickler” grenade launcher for its ease of reloading and explosive power. Some even strip armor off their frames to keep their weight low enough to carry the heavy piece of equipment.||”|
–Mobile Frame Zero: Rapid Attack rulebook, pg. 126
The 'Tickler' grenade launcher is fast to reload because, contrary to appearances, it is not a revolver-style weapon, but a "stacked-projectile" weapon with electronic primer ignition. The trigger assembly is simply latched onto the ammo cylinder, which consists of seven tubes and does not rotate. Each tube holds three grenades, stacked on top of the other, for a full load of 21 grenades. Reloading consists of discarding the entire ammo cylinder and latching the trigger assembly onto a new cylinder.
Sources Main Source: Mobile Frame Zero: Rapid Attack Rulebook