M-920 Cain

The M-920 Cain is a heavy weapon from Mass Effect 2.

In-Game Description
The effectiveness and efficiency of mass-effect-based weapon technology has rendered large-scale deployment of highly explosive weaponry all but obsolete in infantry weapons.

Normandy's scientists have prototyped a modified version of traditional high-explosive rounds that is applied to a 25-gram slug. When accelerated to 5 km/s, the round is devastating. Though a technically inaccurate label, this prototype weapon is nicknamed the "Nuke Launcher," and its high-explosive matrix generates an archetypical mushroom cloud on impact.

It inflicts high damage with large area of effect. Very effective against armor, shields, and barriers.

Acquisition
Unlocked at the Normandy research station after three Heavy Weapon Ammo upgrades have been researched. Costs 25,000 iridium.

Player Notes

 * Very useful against bosses on Insanity.
 * On normal difficulty, the Cain is capable of killing enemies within an extremely large area in a single shot. The Thresher Maw on Tuchanka and the Human-Reaper are the only enemies in the game that the Cain cannot kill instantly. Insanity difficulty adds a few more to the list, Gunships, Praetorians, and the Colossus also do not die in one hit, though each will have very little armor remaining. Instead, the Cain takes off a little more than half of each boss's life bar. On Hardcore and Insanity, the Cain is extremely useful for shortening difficult fights, such as those against Praetorians.
 * Gathering all the heavy weapon ammo you can find will generally allow it to be used once every other mission. However, Cain can only be fired when its ammo count is at 100% or above, meaning that it can only hold enough ammunition to be fired twice (full ammo upgrades bring its capacity to 200%, or 2 shots). If the Cain is shot quickly after the first shot, the charge time would be neglected.
 * It is a devastating weapon. Because of its large damage effect, don't fire it within a small room, and make sure to target an area that is sufficiently far away from you. It WILL kill you. A second problem with this weapon is the long 'charging time' before the weapon fires. It's generally best to 'charge up' the weapon while hiding behind tall objects that have maximum cover from enemy fire without actually having to 'duck' or 'lean on' the object before side-stepping out and unleashing the slug at the last second. Alternatively, if you are an Infiltrator, you may use Tactical Cloak while the weapon charges up, making you invisible for the duration of the charging. This way the shot will be fired just as you are uncloaked.
 * Its single shot capability early in the game makes it a questionable choice, as other heavy weapons are less ammunition intensive allowing them to be used throughout an entire mission rather than saving your one shot for the final boss.
 * After 5 Heavy Weapon Ammo upgrades the ammo will 'refill' automatically after each mission you use it on provided it is equipped at the end of the mission. (confirmed for 360 only)

Trivia

 * The M-920 Cain is the only heavy weapon available for research that does not unlock a codex entry.
 * The real world equivalent is the Railgun, which has clocked speeds at over 2.4 kilometers per second, with a projectile weighing in at 3.2 kg / 7.0547 pounds.