The weapon appears in the first campaign mission, Black Tuesday, and at any point in this mission the XM25's ammo regenerates without the need of an ammo crate when Sandman says to use it to flush enemies out. It also appears in the Spec Ops missions "Flood the Market" and "Smack Town". It differs from the multiplayer XM25 in that it is bolt-action rather than fully automatic, and it doesn't require the player to lase a target for air-burst, as the grenades automatically explode when they are in proximity of an enemy.
Multiplayer
The XM25 is unlocked at Level 52 in Call of Duty: Modern Warfare 3's multiplayer. The XM25 functions differently from a regular grenade launcher - when the player aims down the sights, they can mark the distance to the point they are looking at by pressing the sprint button. After a distance is marked and the player shoots, the grenade will explode upon reaching one meter past that distance. The grenades also have a linear trajectory. Contrary to popular belief, it is actually fully-automatic with a 4 round magazine. The XM25 is the only launcher that can be hip-fired.
Damage-wise, it is almost completely incapable of killing an uninjured opponent in 1 shot, as it's sometimes possible for targets to survive even direct hits, making one-shot kills extremely unlikely. Therefore, multiple shots are frequently required to take out a single enemy. This isn't much of an issue due to the firing speed, but taking fire may cause grenades to fly off course due to flinching. The aiming system allows for a user to fire it through windows to dispatch of any enemies seeking cover behind the sides of the window, making it excellent at eliminating snipers firing from windows. The rate of fire possible allows it to kill any targets that it indirectly hits in a short amount of time over long distances. Despite the decent rate of fire, it is not advised to use the XM25 in close to mid-range in open areas, as without a direct hit, most conventional weapons will be able to kill faster.
This weapon is useful to get Recon Pro, as it has the largest ammo supply out of all the Launchers and can paint one target multiple times without killing him.