From Lexicanum

The Flamestorm Cannon is a large Imperial flamer, more powerful than even the heavy flamer.

Each Flamestorm Cannon spouts a billowing tide of burning promethium into the thick of the foe. This powerful flame weapon can only be found mounted on the sponsons of a Land Raider Redeemer used by Space Marine chapters.¹

Sources

• ¹:Codex: Space Marines (5th Edition), p.83, p.143

Flame Weapons

Imperium	Brazier of Holy Fire • Combi-Flamer • Exterminator • Flamer • Heavy flamer • Inferno cannon • Inferno gun • Incinerator
Chaos Space Marines	Combi-Flamer • Flamer • Heavy flamer
Tau	Flamer
Orks	Burna • Kombi Shoota-Skorcha • Scorcha
Eldar	Dragon Breath Flamer • Flamer