The Barrett .50cal is almost completely unchanged, with the exception of new attachments and a redesigned scope. The only notable change from Call of Duty 4 is that sniper rifles now have full mobility, just like SMGs. In addition, it is the first sniper rifle available to the player, while in Call of Duty 4 it is the last.

The Barrett is capable of firing faster than its non-visual recoil can settle. Firing too quickly makes the Barrett inaccurate as shots will no longer hit the center of the crosshairs. This is most noticeable with the ACOG where visual recoil is reduced over standard optics but non-visual recoil remains. This problem is easily mitigated by simply slowing the rate of fire.

In comparison to its closest rival, the Intervention, this weapon does the exact same damage, but it is statistically better in many aspects. The rate of fire is faster, even when taking recoil into account. It also has double the magazine capacity and less sway while breathing, which makes it steady faster when the player begins to hold their breath.

Trivia

• The Barrett .50cal in Call of Duty 4 uses the Leupold 4.5x14 Vari-X scope, which is one of the only two scopes depicted correctly in the game, the other being the one on the R700.
• The suppressors made for the .50 BMG rifles are much larger than those seen on the Barrett .50cal in Modern Warfare 2. These suppressors mostly suppress the muzzle flash, not the sound.
• The PTRS-41 in Call of Duty: World at War is considered to be the Weapon Equivalent to this gun.
• The Barrett .50cal has the same reload animation and firing sound in both Call of Duty 4: Modern Warfare and Modern Warfare 2.
• Like the WA2000, the Barrett has a Mr. Yuk sticker on the lens cover.
• In real life, this weapon is not used as it is in-game, due to its considerable weight and size. Instead it is used as a anti-materiel rifle by all branches of the US military, as well a number of other armed forces across the world.
• The Barrett .50cal has far less recoil in campaign than it does in multiplayer.
• The M82A1 model used in both games is strange as many users upgraded to the M107 Barrett model, although the M107 only has a few minor changes from the M82A1 for the purposes of a video game.
• In Modern Warfare 2, the Barrett .50 cal can be found twice in the single player campaign. It is found in the mission Of Their Own Accord in the room where you must destroy the enemy vehicles. This version has a thermal scope instead of a sniper scope. However the weapon is immobile, similar to the way it was in One Shot, One Kill, including the zoom function and unlimited ammo. It is found again in Loose Ends in one of the basement rooms in the safe house. Unlike the version found in the earlier level, this one can be carried and used freely.
• The Barrett .50cal is used extensively in Special Ops missions containing Juggernauts, excluding High Explosive.
• During Special Ops missions featuring Juggernauts, it is advised to keep this weapon, as it has a good rate of fire, will always stagger a Juggernaut, and can even make Juggernauts stumble sometimes. However, if they do stumble, keep in mind that they are invincible until they get back up.
• The Barret .50 cal's front iron sight is incorrectly shown flipped up in CoD4, while in Modern Warfare 2, it is folded down.
• There is a fingerprint that is barely visible on the gun in the right lighting
• When firing the Barrett from the hip, it is possible to see the handle and the Mr. Yuk sticker move.
• Although it is a lot more effective at distance, the Barrett can make a somewhat effective close quarters weapon, if there is absolutely no time to switch to a secondary, or knife. It can be fired very rapidly, and with its high power is likely to kill in one hit. Steady Aim is very helpful when doing this.
• In the CoD4 single player campaign, it seems that the bipod is in both the deployed and undeployed position at the same time