We’re not going to spend too much time discussing the Quad Launcher here, because it just isn’t that unique a weapon in Fortnite. It functions in the game as a sort of hybrid between the grenade launcher and the rocket launcher. It carries more rounds than the rocket launcher (four, as the name suggests, but not as many as the six rounds that the grenade launcher carries). It can shoot a little farther than the grenade launcher, especially if you point it up at an angle, but it can’t shoot nearly as far as the rocket launcher. As far as damage is concerned, it has a DPS on par with the other two, though it’s a little less powerful than both.
However, as with the grenade launcher and rocket launcher, the Quad Launcher does seem to be very similar to a real-life weapon: the M202 incendiary rocket launcher, developed by the United States during the Vietnam War. The M202 looks more or less identical to the Quad Launcher in the game, even including the fold-down cap on the front. It also takes a four-cartridge clip of rockets.
The real M202 was never made with explosive rounds like the ones used in the game, which explode very similarly to the rounds used in both the rocket launcher and the grenade launcher. Instead, the M202 fired incendiary rockets, and was used by the US Army as a replacement for the World War II flamethrower.
Basically, when the M202’s round hits its target, instead of sending out a shockwave of hot gas that blows up anything in its immediate vicinity, it spreads a chemical in liquid form that sticks to anything it touches and begins to burn as soon as it comes in contact with the air.
It is also worth noting that the M202, while it does use rockets that look rather similar to those used by the rocket launcher, does not have a booster rocket like the RPG-7 does. Instead, when you fire this type of quad rocket launcher, the round is propelled by a single solid fueled rocket motor that works very much like the hobby rockets you might fire in your backyard, in which a solid fuel is ignited and burns very fast for a short period of time, propelling the projectile forward.