History of Clown Cartridge

Clown Cartridge is a weapon perk with the in-game description "Reloading this weapon randomly overfills it from reserves to an improved degree." In practice it randomly gives a reload more rounds than the magazine normally holds (community descriptions say it triggers on a manual reload, not on stow or reloads from other effects).

Weapons

• Interference VI, a Legendary Grenade Launcher reintroduced in Season of the Worthy. Destinypedia notes it was the first grenade launcher able to roll Clown Cartridge. It is the most common trait on that weapon and is often paired with Full Court.
• Crux Termination IV, a Rocket Launcher from Season of the Wish, can also roll it (Destinypedia).

Interference VI's season is listed as Season 10 by the D2 Wiki and as Season of the Worthy by Destinypedia; these agree.