From Destinypedia, the Destiny wiki
Avalanche is a Legendary Machine gun that was introduced in the 2018 Dawning event. It is the first Machine gun developed by SUROS. Like the Thunderlord and Hammerhead, it is an Adaptive Frame Machine gun. It could be found almost anywhere in The Dawning events, from treats to the vendors and characters or random packages.
Although the Avalanche is an Adaptive Frame Machine gun, has the same Impact, and even fires at the same Rounds Per Minute as the Hammerhead, it just isn't as good as most Hammerhead rolls have better perks than Avalanche. The main problem being that the stability, handling, range, and reload speed don't match the Black Armory Machine gun.
List of appearances