Vostu-pattern carbine

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The Type-51 Carbine, also known as the Covenant Carbine, is a Covenant infantry firearm, carried commonly by the Jiralhanae, Kig-yar and Sangheili.

Design Details
The Type-51 Carbine is a Covenant recoil-operated and charger-fed, semi-automatic weapon. The Type-51 Carbine serves as the Covenant's medium to long-range weapon and fires a 8mm caseless radioactive projectile. The weapon's design is very basic, with unique differences. The first is its magazine placement, which is located right above the trigger guard - the weapons cylindrical magazine hold 18 rounds, and also provides indication of number of rounds left in the magazine, using holographic display. The back end of the weapon contains two circular openings, the forward one is the weapons hand guard and the area in front of it is where the weapons trigger is located. On the weapons top rail is the magazine receiver and loader, below it is a hammer like device which springs back when the weapon is fired. The forward part of the weapons contains the Type-51 Carbine's barrel which itself is well insulated to protect the shooter from the harmful radiation released from the round. The weapon also is capable of 2X magnification, however it is not known where the magnification device is located. Kig-yar Marksmen are known to use this as a marksmen rifle and can be used to assassinate or pick off unsuspecting officers with the weapon's long-range capabilities. Sangheili Spec-Ops and regular Sangheili infantry are known to carry it into battle as a medium range weapon, as well as Jiralhanae infantry.

Ammunition
The Type-51 Carbine marks itself as unique among Covenant firearms by its ammunition. Rather than using Plasma bursts which can be inaccurate and slow at long range, this weapon utilizes caseless radioactive projectiles, shot out at supersonic speeds. It is unknown how or when the Covenant developed this weapon, but its ammunition is believed to be based off of the Type-33 Light Anti-Armor Weapon's ammunition. When fired, the projectile is powered along its entire flight path, consuming up to 50% of its total mass by the time it reaches its maximum effective range. Against light armored targets, the rounds' supersonic speed and super-heated nature ensures armor penetration on either the first or second impact. Impacts to the flesh can vary dependent upon range and speed - a single round impacting flesh at close range will penetrate deep into the target, and can nick bone. The kinetic energy from the impact of a round at close range can knock back an individual. Two rounds that impact the same area at close range will pass through the target easily. At longer ranges the damage and kinetic impact is weaker. After a round comes to a halt inside the target's body, the round will continue to burn the victim's innards until the properties of the round has cooled. However, the aftermath of being struck with a round from the Carbine is moderate-to-severe due to the round's radioactive nature. A surviving victim will require additional radiation treatment to ensure survivability. In the Halo Trilogy, the Carbine's strength and lethality is compensated for the sake of gameplay and ESRB rating.

Advantages
The Type-51 Carbine, with its 2x zoom ability is an excellent ranged weapon. Its accuracy and performance in the field makes it a up front choice for infantry who are required to engage enemy infantry at medium range. Its fast rate of fire is useful against more heavily armored infantry is able to disable any type of infantry energy shield system including Jiralhanae Power Armor, Jackal Point Defense Gauntlets or Stationary Shield Generators. The Type 51 Carbine also fits the role of a marksmen weapon, as it can be used to take out a target from medium range - this with the added bonus of low noise emission allows the carbine to perform multiple roles in the field.

Disadvantages
The Type-51's rounds give off a light green trail, giving away the position of the shooter, a trait similar to the Type-50 Sniper Rifle System's trail. Its distinct sound at close to medium range may also attract the attention of nearby enemy infantry. Its firepower when compared to the human infantry counterpart the Battle Rifle, is weak, so it usually only gives an advantage to more skilled infantry. The Type-51, if fired too fast becomes inaccurate making it less likely for the shooter to take down a target. Its magazine is also relativity small and may not be enough and when faced with infantry with energy shielding will require almost an entire clip to eliminate the enemy.

Changes from Halo 2 to Halo 3

 * In Halo 2, when you zoom in, the view is a group of seven hexagons melded into a honeycomb shape. In Halo 3, four lines will separate from the center in addition to the hexagons, almost on the same plane as the reticule lines.
 * In Halo 3, the Carbine has a green patterned circle on top of the magazine indicator.
 * Carbine ammo is much more abundant, double the amount usually given in Halo 2.
 * Improved design, including more polygons and better textures.
 * New sound effects for the carbine.
 * The power has been reduced slightly from its Halo 2 counterpart. It now takes eight shots to kill a fully-shielded opponent in multiplayer, presuming the last shot is to the head, as opposed to seven shots in Halo 2.
 * In addition to the reduction in per-shot damage, the Carbine also starts with two spare magazines when found in multiplayer, whereas it only started with a single spare magazine in Halo 2 multiplayer.
 * Emits a small cloud of gas when reloading.

Campaign

 * 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.
 * 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, the Covenant Carbine will easily take down Grunts from close to far range. Simply aim for the head. However, if you aim for the body, it will take 4-6 shots, decreasing its effectiveness.
 * If the Jackals 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, you should 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.
 * 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 it firing on you, simply shoot it at the head.
 * Like the human sniper rifles 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, you can combine the Carbine with a Plasma Pistol that takes out shields while the Carbine will finish your enemy off.

Multiplayer

 * 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 you want to ride in the passenger seat of a vehicle. Since you are unable to scope in a vehicle, the Battle Rifle's spread would cause many rounds to miss its target. A Carbine is not severely affected by this problem.
 * Combine the Carbine with a Battle Rifle can continue your blitzkrieg, when you run low on ammo in one weapon, switch to the other.
 * 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 you play campaign or multiplayer in Halo 3, the Carbine is in fact less accurate at long range than the Battle Rifle. You can see this very easily in Sierra 117, after you clear out the Sniper Alley, as Sgt. Johnson says "C'mon, you dumb apes".  There are a number of Jackal Snipers in that area.  Killing them at range is better done with the Battle Rifle than the Carbine due the Carbine's inability to fire perfectly straight like the Battle Rifle.  Covenant AI seem unaffected by this phenomenon.

UNSC Remarks

 * “So — it’s just their projectile weapons that we’ve figured out how to reload? I guess I’m cool with that.”
 * “It’s almost a direct analog of the BR55. I just wish it had a more — um — conventional scope.”
 * “In my youth I used to board Olympus a couple o’ times a year—you see where I’m going with this? Yeah. That foxtrot gun is the size of my old board.”
 * “Oh man! You really need to learn to recognize the symbols on top of the charger—and count your shots, too. First time I picked one up I just about brained myself when it ejected.”
 * “Wish it was smaller; wish it had a proper stock—or at least a butt pad.”
 * "Hey — don’t inhale immediately after the charger ejects. I heard that shit will give you Boren’s Syndrome." (There are no conclusive tests that indicate that the Type 51-Carbine put the user at risk for contracting Boren's syndrome.)

Trivia

 * In the Halo 2 and Halo 3 instruction booklets, the Carbine is incorrectly labeled as having 36 rounds, instead of the actual 18 rounds. Ironically, this is the number of rounds the Carbine's human equivalent, the Battle Rifle, has.
 * The green ring on the end of the magazine is an ammo indicator and is effective when you need to keep your focus on the actual battle.
 * In Halo 2, on the level Sacred Icon, there is a glitch where you start off with 78 spare rounds instead of the usual 72. However, if you empty the magazine and then try and pick up Carbine ammo, you will only be able to get a total of the usual 72 spare rounds.
 * If you give a shield-bearing Jackal a Carbine in Halo 2 and then melee it, it will drop the Carbine and pull out a Plasma Pistol. This is done for the Unlimited Plasma Pistol Glitch.
 * If you give a shield-bearing Jackal a Carbine in Halo 2, it will hold both the Carbine and its shield in either hand, and the Carbine will protrude from the shield in an erratic manner.
 * In Halo 2, when you reload, the magazine will pop out but disappear almost immediately. In Halo 3 they will fall on the floor and take a short while to disappear.
 * In the level, several Carbines have 120 rounds in reserve, much more than the usual max, 72. This also occurs on other levels, especially if the Carbine is taken from an ally scripted to pick the weapon up, such as the Marines in the detention block in Gravemind.
 * In the Halo Wars official strategy guide, the Covenant Carbine is called a "slug beam rifle", probably because it fires radioactive rounds at rather high velocities and at long ranges.
 * The designer's idea of the Type-51 self-ejecting the spent magazine might have come from the WWII-era M1 Garand's en-bloc clip.
 * In Halo 3: ODST, the Carbine has a different firing sound, sounding much deeper than before.
 * The Carbine is arguably the best non-power weapon available in ODST's Firefight mode. This is due to both the removal of the Battle Rifle from the game and the Carbine's status as a headshot-capable energy weapon, which makes its rounds immune to the adverse effects of the Tilt Skull.
 * The portion of the clip that faces the player resembles a smiley face with a gap in the mouth.
 * The Covenant Carbine will not return in Halo Reach, as it is replaced by the Needle Rifle, which shares a few similarities with it but fires needles instead and explodes if supercombined (3 shoots needed with the shields down).