Cryo Round technology is used to modify standard weapon slugs. A cooling laser collapses the ammunition into Bose-Einstein condensate, a mass of super-cooled subatomic particles capable of snap-freezing impacted objects.
Normandy's scientists have found a way to apply this technology on a large scale: by generating a mass effect containment "bubble", this proof-of-concept large weapon technology is effective against armor, shields, and biotic barriers. It is nicknamed the "Cryo-Blaster".
An EXTREMELY effective heavy weapon for those that intend to use them a lot, holding the weapon out does NOT slow you down unlike other heavy weapons. Additionally, you can hold twice as many rounds as compared to the grenade launcher, and therefore allows for many rounds to be fired quick succession.
Very effective against shielded groups of enemies, e.g. Husks will die spontaneously after freezing.
Repeated hits will strip off shields, barriers, and armor. Once unprotected, enemies, even heavy ones like YMIR mechs and Geth Primes, can be frozen for at least 15-20 seconds, leaving them open to further attacks from which they will suffer double damage.
It takes a short while for the projectiles to reach their target, and a single hit does little damage, but the generous ammo capacity partly compensates for that.
In order to freeze an enemy, the target must remain in the freezing cloud, making it mainly a defensive support weapon. On the other hand, the freezing cloud may trap several enemies at once, providing an area effect.
The Avalanche can be fired rapidly or charged up, although a charged blast is no different from a non-charged blast.
It isn't a good idea to bring this weapon into confrontations with the Blood Pack, as the freezing effects don't stop regeneration, and the little damage it does won't be enough to make a dent in enemy numbers. However, Krogan can be much easier to kill once frozen.
The M-622 Avalanche does not cause any type of splash damage to Shepard or the squad, regardless of difficulty setting, allowing it to be fired at point-blank range safely (one of four heavy weapons capable of this; though what the Collector Particle Beam and M-451 Firestorm lack in splash damage they make up for in higher single target damage and note that the Arc Projector must hit an enemy in order to shock other, nearby ones).
The projectile fired by the M-622 Avalanche can sometimes ricochet off of squad members it is fired at.
The Avalanche produces a large blast radius of 5 Meters.
The weapon is particularly effective at dealing with the Praetorian on the Collector Ship on the Insanity difficulty setting. Moving positions often makes Shepard vunerable to flanking fire from Collector Drones or from Husks. The Avalanche can easily freeze them with four or five well placed shots which will allow the player and his squad time to either take them out or focus fire on the larger threat. This uses minimal Heavy Weapon Ammo which also leaves Shepard with plenty of spare rounds for the swarm of Husks that appear at the end of the mission.
The above tactic also works well against other heavy unit types such as YMIR Mechs, Harbinger, and Scions. However, these units do fall significantly quicker than a Praetorian even on the Insanity difficulty setting.
If Shepard or a squad member is about to be swarmed by Husks the Avalanche can be deployed on top of your own positions to quickly kill them.
This weapon is particularly effective with Grunt in your squad as his charge may then shatter your frozen foes.
The Avalanche's projectiles are affected by gravity, allowing them to potentially hit enemies that are behind cover.
Although holding the fire button charges up the weapon, it does not have any effect on the weapon. This could possibly have been an early feature that was removed.
The Avalanche, like many other Heavy Weapons from Mass Effect 2, was originally intended to appear in Mass Effect 3, as a screenshot shows Shepard using it on an Atlas during the Sur'Kesh mission, but it was cut late into development. The heavy weapons that were cut still remain in the game's coding.