AIE-486H machine gun

The AIE-486H Heavy Machine Gun (abbreviated AIE-486H HMG or simply HMG), more commonly referred to as the Heavy Machine Gun Turret, is a United Nations Space Command ground weapon effective against infantry and light vehicles.

Design Details
The AIE-486H Heavy Machine Gun is a standard Gatling-style heavy machine gun, used by the UNSC for offensive and defensive purposes. It is also more powerful than the UNSC's stationary turret, the M247 GP Machine Gun. It has saved many lives with its defensive capabilities holding enemy forces at bay for a limited time during the battle of Reach, accounting for many casualties to the Covenants efforts to take out the Orbital MAC Generators.

For defensive purposes, it can be mounted on a tripod, but when used for an assault it can be irreversibly and quickly detached from it's tripod. In its unmounted form, the weapon has a limited ammunition capacity of 200 rounds and takes about a second to "spin up" before reaching its highest rate of fire. Pulling the trigger once will cause the gun to fire a maximum of two rounds at a moderate rate; holding it down builds up the rate of fire to a higher rate.

The gun slowly climbs during automatic fire like the M7 Caseless Sub Machine Gun, but its recoil is lessened by the gun's weight, which makes it hard to move around as well as decreasing the user's speed. Unlike most mini-guns in other games, the AIE-486H does not overheat with continuous fire. This is a more realistic feature as having three barrels on the gun disperses the heat equally within each barrel, allowing the gun to remain cool and continue functioning.

Ammunition
The AIE-486 fires 7.62x51mm Saboted Light Armor Penetrator rounds at a high rate of fire. The SLAP design incorporates a polymer sabot, which allows for the use of a tungsten penetrator projectile of a lesser diameter than the original bore. By using the casing of a large cartridge with a lightweight projectile, the velocity of the projectile is greatly increased. The bullets are powerful enough to punch through the armor of a Warthog or a Wraith and destroy it with ease.

Advantages
The AIE-486, like all machine guns, packs a powerful punch, filling the air with many rounds at a high rate. The AIE-486 is mainly a Support Weapon; however, its offensive and defensive capabilities contradict its supportive nature. The AIE-486 is extremely effective against Covenant forces, and is strong enough to take down a fully armored and shielded Brute or Elite within about 5-10 seconds of continuous fire. A SPARTAN-II or most ODSTs is strong enough to forcefully detach (or more accurately rip) the turret off of its mount, in opposition to dismantling the tripod and gun with tools. Once detached, the player will appear in a third-person view, although the regular targeting reticule is still apparent.

Disadvantages
In its stationary form the AIE-486 is a basic death trap if its user is flanked from multiple locations. Once detached from its tripod the AIE-486 has a limited ammunition supply, and once it runs out the turret must be discarded. In Halo 3, there is no physical way to reload the turret or remount it on the tripod. While wielding the turret, a Spartan II or Elite will move or strafe significantly slower than their normal speed. This could be due to the mass of the turret or, perhaps, a gameplay mechanic implemented for balancing the gameplay.

Campaign

 * On higher difficulties it is key to detach the turret; being stationary, the enemy will be able to flank you or fire on your position with ease.
 * During the most difficult encounter on Tsavo Highway (Level) it is key to detach the turret and pull to the back of the buildings and begin taking down jet pack Brutes, then if the opportunity presents itself lay into the chieftains with it.
 * Taking advantage of the AIE-486 on Crow's Nest (Level) during both the hanger encounter and the Landing Pad Bravo encounter, the turret will work well at chipping away at the jet pack Brutes' shielding, allowing your allies to take them down more quickly.
 * In both Campaign and Multiplayer, a player model carrying a detached turret moves faster when moving diagonally or sideways.

Multiplayer

 * The Machine Gun Turret is not as powerful as the Warthog's LAAG, so be careful when taking on an undamaged, unengaged Warthog, or else you'll quickly wind up dead. Only fire upon Warthogs that haven't seen you and are concentrating elsewhere.
 * A way of moving faster with the turret can be done by constantly dropping and picking up the turret. This, while looking like you're dribbling the gun, allows almost normal movement. Be aware of other weapons lying around, as you might pick one of those up instead.
 * HMGs are easily detached using explosives. A good tactic is to grenade the turret instead of detaching it to reduce the amount of time in a stationary position.
 * Detaching the turret in Multiplayer has its advantages and disadvantages. You will move more slowly, making you more vulnerable to small arms fire and grenades. It is tactically wise to only use the turret in defensive situations that will provide good cover. If you have the opportunity to use the turret on offense be sure to have another player backing you up as you lay into the other team.
 * The turret is one of the best defensive weapons to use on Avalanche, High Ground, Last Resort, and Sandtrap during objective based games.
 * Remember to not stay on the turret too long in sniper matches!
 * Breaking a turret without using any weaponry is made easy by standing on top of it, crouch-jumping, and letting go of the crouch button before you hit the ground.
 * Do not underestimate the power of leaving the weapon attached to its mounting. While mounted ammunition is effectively unlimited and thus the weapon can produce a tremendous volume of firepower. This can be effective at tactically suppressing particular fire zones from enemy advance, and forcing snipers to keep in cover. It will draw a great deal of the enemy's attention, forcing them to expend strength trying to counter it.
 * If engaged in a team match, it can be wise to occupy the weapon while mounted if one has a team mate to watch the flank. This team mate can help pick off enemies that the turret cannot reach and to warn the team mate operating the turret when the enemy is moving in on the flank so that both can relocate or deal with the threat.

Trivia

 * Although it is called a Heavy Machine-Gun, the 7.62x51mm NATO round it uses would actually classify it as a medium machine gun.
 * Like the M41 LAAG, the AIE-486H bears a striking resemblance to the GAU-19/A machine gun used by the United States military. The GAU-19 and AIE-486H both share the same distinctive flash suppressor. Unlike the GAU-19, which fires .50 BMG (12.7x99mm) rounds, the AIE-486H fires the 7.62x51mm Saboted Light Armor Penetrator rounds.
 * The AIE-486H fulfills the same defensive role of the GAU-19/A, being mounted on aircraft like the Pelican, reminiscent to the GAU-19/A being mounted on a modern-day helicopter.
 * During Forge matches, the mounted AIE-486H can be picked up, moved, and rotated, even while another player is using the turret. If the other player rips the turret from the base while this is happening, the player will duplicate the turret. This can be used to arm an entire team with turrets. These traits also apply to Plasma Turrets, and anyone seated in the turret position of a vehicle won't be forced out like the driver will.
 * Brutes will occasionally utilize Heavy Machine Guns against players and allies, the most common example of this appears in the level Crow's Nest, in the Armory.
 * It is possible to use the machine gun mounted in the back of a Pelican in Halo 3 by killing the NPC manning it and getting into the drop bay.
 * On the base of the empty shell casings, the words Chief-EGX can be seen. This is apparent on all of the UNSC weapons that eject shell casings.
 * If you put a detached turret into the tunnel in High Ground, then crouch in the tunnel and pick up the turret, you will be standing, meaning that you have shrunk to half-size.
 * The AIE-486H's first mention may in fact be in Halo: First Strike, in which the surviving Marines and Spartans of Red Team use chainguns, among other defenses, to keep the Covenant from compromising one of the orbital defense platform generators on the surface of Reach, though, technically speaking, a chaingun is a fixed-position, single-barrel machine gun, and a gatling-/mini-gun has 3+ rotating barrels.
 * While the AIE-486H HMG might appear more mobile than the Halo 2 turret, it is shown to be heavier and harder to carry, even slowing Spartans and Elites. The M247 General Purpose Machine Gun (from Halo 2) is actually lighter in its portable form; it is able to be carried by Marines as seen in the levels Cairo Station and Outskirts, and the stationary form doesn't appear difficult to rip off.
 * The AIE-486H is usable in Halo 3: ODST in its detached state, just as it is in Halo 3. This is done for gameplay reasons only, as an un-enhanced human should not be strong enough to pick the turret up, much less carry it around and fire it accurately on the move.
 * the Marines in Halo 3 ODST call it a .50 cal even though it uses 7.62x51 nato round

Internal

 * Plasma Cannon
 * M247 GP Machine Gun