In Halo 2 because Brutes have very little head protection, a skilled player can take out three or four Brutes with one magazine or with one shot to the head when playing on easier difficulties. Its fast rate of fire is useful to shoot off a Brute's helmet and then shoot a Brute's head in less than a second. Ammunition for the Carbine is also more prevelant than its UNSC counterpart, particularly in later levels of the game.
In Halo 3, since Brutes have better armor, the above tactic is not as effective; however, due to the Carbine being an energy weapon and a projectile weapon, it is better at removing Brute Power Armor than the Battle Rifle.
As with the Battle Rifle and the Needle Rifle, the Covenant Carbine will easily take down Grunts from close to far range. Simply aim for the head. However, if shot at the body, it will take 4-6 shots, decreasing its effectiveness.
If you encounter Jackals that are on patrol or have their back turned to you, simply aim for the head and pull the trigger, resulting in a one-hit kill. However, if in the middle of a firefight, instead run up towards the Jackal, melee it or shoot the exposed hand which should make it flinch and take away its shield for an instant, and kill it with a headshot. Carbine rounds will inflict damage on the Jackal's personal shield, causing the shield to collapse within 4-10 shots depending on the difficulty and providing you with a clear shot at their head. However, unlike with the plasma rifle, the damage done is not enough to actually collapse the shield with a reasonable amount of shots and is rather wasteful of ammo.
Jackal Snipers are relatively easier than normal Jackals due to the lack of shielding, however they can be still lethal as a single shot can kill you in Legendary. To avoid this problem, simply shoot it before it can shoot you. Often times they will drop Carbines, allowing you to replace your depleted ammunition.
Like all sniper weapons in the Halo trilogy, the Covenant Carbine will leave a visible, green trail that gives away the position of the shooter. In dark or chaotic areas, this will help you determine where your enemies are.
Due to its power and its ability to headshot, you can combine the Carbine with a Plasma Pistol that takes out shields while the Carbine will finish your enemy off.
The Carbine in Halo 4 operates almost exactly as its previous incarnations do. In addition, it is also effective at eliminating Promethian Watchers thanks to its shield-stripping capabilities and fast fire rate.
The Carbine's magazine, though holding half as much ammo than the Battle Rifle, will last longer because the Battle Rifle fires in bursts of three, emptying a magazine with twelve pulls of the trigger. The Carbine fires one round at a time, requiring eighteen pulls of the trigger to empty a magazine.
This is a better choice over the Battle Rifle when riding in the passenger seat of a vehicle. Since the rider cannot use the scope, the Battle Rifle's spread would cause many rounds to miss its target. A Carbine is not severely affected by this problem.
Combining the Carbine with a Battle Rifle lets a player take advantage of having two precision weapon, letting them switch until ammo can be found.
The Carbine, when used correctly, can take down an enemy slightly faster than a Battle Rifle. However, it requires more aim, taking at least seven shots to the head in Multiplayer. Damage done by the Carbine is slightly lower than that of the Battle Rifle, but it fires about twice as fast, making it almost as effective. Experienced players would prefer the Carbine over the Battle Rifle because of the constant shifting of aim required.
Regardless of whether playing campaign or multiplayer in Halo 3, the Carbine is in fact less accurate at long range than the Battle Rifle. However, it is more effective at close range, due to its higher rate of fire and better hip-fire characteristics.
In Halo 4, the Carbine is more equal with the Battle Rifle in terms of firepower.