Extended Mags

Extended Mags (shortened from "Extended Magazines") is an attachment available in Call of Duty: World at War, Modern Warfare 2, Call of Duty: Black Ops, Call of Duty: Modern Warfare 3, and Call of Duty: Black Ops II. It increases the ammo capacity of the weapon it is attached to by around 40%-100%.

Call of Duty: World at War
The Extended Magazine is an attachment available for all submachine guns and the M1A1 Carbine in Call of Duty: World at War multiplayer. The attachment doubles the magazine capacity of a given weapon.

Variants
There are five weapons which accept Extended Magazines; however, there are different variants of the attachment.

Round Drum
The Round Drum is available for the Thompson and the PPSh-41. It is unlocked after the Marksman III challenge for the Thompson and after the Marksman II challenge for the PPSh. It is the PPSh-41's most common attachment; its high rate of fire means the smaller magazines need frequent reloading; and also, the attachment is unlocked at the Marksman II Challenge, meaning it is easier to unlock.

Box Magazine
The Box Magazine is available for the M1A1 Carbine and Type 100.

Dual Magazines
The MP40's Extended Magazines attachment is called Dual Magazines. It is by far the most-commonly used attachment on the weapon, as it allows constant firing for roughly 8–9 seconds.

The attachment is titled "Dual Magazines" but it just adds the ability to use two magazines as one, therefore doubling capacity from 32 to 64 bullets.

Call of Duty: Modern Warfare 2
The Extended Magazines return in Call of Duty: Modern Warfare 2. It's unlocked by getting 40 bullet penetration kills while using FMJ rounds for primary weapons, or it is obtained by getting the last marksman challenge for handguns, machine pistols, and shotguns. It is compatible with all weapons in the game except for the launchers, the .44 Magnum, Desert Eagle, Model 1887, Ranger, and the Riot Shield.

The increase in magazine size that is given depends on the gun. Generally, it increases magazine size by 50%, but with some weapons it can increase magazine size by a greater amount. The attachment also does not increase starting ammo capacity unless paired with Scavenger Pro. A recommended weapon type to get Extended Magazines for is light machine guns, being that they have enormous ammo capacities, and the best penetration in the game. However, it is not recommended with assault rifles or SMGs, because most players tend to reload after each kill, though it can be useful if the player does a lot of spraying. The P90 becomes almost similar to a light machine gun with Extended Magazines due to its already large 50 round magazine being turned into a 75 round magazine, which allows the user to hold down choke-points, but has a much quicker reload than the LMGs. While using Extended Magazines on the P90, a player can sprint for a longer period than normal (patched on PS3/X360, still available on PC). This allows users to equip another first tier perk instead of Marathon like Sleight of Hand or Bling. The P90 is the only weapon which gains this advantage. The AA-12 in particular has a very small magazine to balance it, so Extended Mags (which doubles its capacity to 16 shells) are extremely popular among those who have unlocked it.

Call of Duty: Black Ops
Extended Mags returns in Call of Duty: Black Ops, and is available to the player. It can be used on nearly all weapons. This attachment is not to be confused with Dual Mags, which is another attachment in Call of Duty: Black Ops that decreases reload time by taping 2 magazines together.

Unlike in Call of Duty: Modern Warfare 2, the magazine model changes when Extended Mags are used, just like in Call of Duty: World at War. A notable example of this are the HK21 and RPK, where they will be given drum magazines and be called "HK21 Drum Mag" or "RPK Drum Mag." The M60 is also given the name "M60 Big Ammo." Other weapons will be shown using longer magazines. The exception to this are the M14 and the M60, which do not use a different magazine model.

Due to balancing purposes, a weapon cannot accept Extended Mags and Dual Mags at the same time by using Warlord. Rapid Fire cannot be paired with Extended Mags either.

Call of Duty: Modern Warfare 3
The Extended Mags returns in Call of Duty: Modern Warfare 3. It increases magazine capacity, and now increases the starting ammo count as well, instead of previously decreasing spare ammunition and putting some rounds into the first magazine. Extended Mags also increases the maximum amount of spare ammunition a player can hold. It almost always increases magazine capacity by 50%, with only 3 exceptions: the AS50, L118A and MSR at 40% increases (although the ammunition in reserve for these 3 sniper rifles is actually increased by 50%).

It is unlocked at Weapon Proficiency Level 10 for Machine Pistols and certain Pistols, Weapon Proficiency Level 15 for Sniper Rifles, Weapon Proficiency Level 24 for SMGs, Weapon Proficiency Level 25 for LMGs and Weapon Proficiency Level 26 for Assault Rifles and Shotguns.

Prior to the January 25 update, there existed a bug for Extended Mags that when equipped on a Shotgun, the weapon would shoot 50% more pellets per shot, effectively increasing damage and consistency in addition to the standard effects of the attachment. When the Extended Mags attachment was combined with the shotgun-exclusive Damage Proficiency, it would produce a staggering 210% increase in the damage output of the base version. It has now been patched.

Call of Duty: Black Ops II
Extended Mags returns in Call of Duty: Black Ops II as Extended Clip. The attachment like before increases the magazine's capacity, however, the capacity is only increased by 33 % (one third), no longer by 50%. Fortunately, the attachment still gives extra ammo.

Trivia

 * In Call of Duty: Modern Warfare 2, the Extended Magazine Create-a-Class picture uses the AUG HBAR magazines, in Call of Duty: Black Ops, it uses the Galil magazines, and in Call of Duty: Modern Warfare 3, it uses the Type 95 magazines.
 * Extended Mags only affects the reload time in World at War, and shotguns that are reloaded one shell at a time.
 * Using Extended Mags on all LMGs, except the AUG HBAR, in Call of Duty: Modern Warfare 2 will have all ammo in one magazine, which means the player does not have to reload, unless the player is using Scavenger or picks more ammo.
 * All LMGs, except the AUG HBAR, with Extended Mags in Call of Duty: Modern Warfare 2 have so many rounds in one magazine (200) that on the HUD, the bullet count overlaps the white bar that separates ammo and equipment indicators.
 * In Nazi Zombies for Call of Duty: World at War, the PPSh-41 is the only weapon to have the Extended Mags attachment.
 * In Call of Duty: Black Ops, when Extended Mags is used on the AK-47 or the AK-74u, they use the normal magazines used by the RPK, although the RPK's magazines have a 40 round capacity and the Extended Mags for the AK-47 and AK-74u have a 45 round capacity.
 * The Mission Mode challenge Smack Town in Call of Duty: Modern Warfare 3 was the first time this attachment was featured in Special Ops, being used on an M4A1 Grenadier.
 * Unusually, the Elite icon for Extended Mags in Call of Duty: Black Ops displays a regular AK-47 magazine, not an extended magazine.
 * In the Wii version of Black Ops, extended magazines not only increases the number of rounds without reloading, but also increases the player's reserve ammo capacity.