HK21

The  is a light machine gun featured in Call of Duty: Black Ops.

Campaign
The HK21 is the secondary starting weapon for Hudson on the level "Rebirth." It is very powerful and usually kills in one or two shots to the torso, and has the ability to gib most enemies. It can also be found in other missions, such as "Numbers" and "WMD". Rarely, it can be found with a Round Drum, which gives the player 80 rounds per drum, making for a very effective weapon.

Multiplayer
The HK21 is unlocked at Level 2 to the player, as part of the default LMG class.

The HK21 will kill in 3 shots at any range, or in 2 consecutive headshots, and has medium recoil. It also has no damage drop off at range. This makes the HK21 extremely powerful at medium to longe range. Long-range encounters can be dealt with by firing in small bursts. The HK21 is tied with the Stoner63 for the smallest capacity out of all the LMGs so the Extended Mags attachment is extremely useful, as it doubles the ammunition capacity to 60 rounds. The iron sights, while clear and open, can be difficult to use for some. For this reason, some players may find the Red Dot Sight or Reflex Sight useful.

Because the HK21 has very low movement speed, perks like Lightweight can be effective to use with this weapon. Scavenger is recommended for providing prolonged fire, which is commonly combined with the drum mag. Flak Jacket Pro is always excellent for an LMG class, as enemies' explosives will be less likely to kill the player. Steady Aim benefits the HK21 as it improves its CQB capabilities and is useful if caught off guard. Tactical Mask Pro will prevent special grenades from disorienting the player, which are commonly thrown at choke points. Sleight of Hand can also be very useful for this weapon, as it dramatically reduces the amount of time needed to reload, as well as improving ADS speed with the Pro version. Warlord can be used to combine the drum mag with an optic of choice, allowing for easier targeting at close or long range. Hardened is a very useful perk for any of the LMG's, as it will allow the HK21's normally high damage to carry through enemy cover.

Attachments

 * Extended Mag (Drum Mag)
 * ACOG Scope
 * Red Dot Sight
 * Reflex Sight
 * Infrared Scope

Zombies
The HK21 can be found in the Nazi Zombies game mode and can only be obtained from the Mystery Box. It starts with a magazine size of 125 rounds and with an extra 500 rounds. When Pack-A-Punched, it becomes the' "H115 Oscillator" This increases the magazine size to 150 rounds with 750 extra rounds, and gives an increase in damage. The HK21 is somewhat similar to the RPK, but sacrifices a low rate of fire for a larger magazine, higher damage, and higher reserve ammo.

Due to this weapon's high power and large magazine, it is arguably one of the best non-Wonder Weapons in Zombies Mode.

The low rate of fire, very high magazine size and high reserve capacity makes ammo less of an issue for the HK21 than for other weapons. However, the very slow reload time makes Speed Cola useful when using this weapon. Double Tap Root Beer is also useful from rounds 18+ because of the HK21's low rate of fire. The HK21 also hinders the player's movement speed; however this can be rectified by using Stamin-Up. The HK21 can be viewed as a "love it or hate it" weapon. Some will love the high ammo, but the low rate of fire and movement speed will deter others from using the weapon. You'll want to at least have a light secondary weapon for situations where speed becomes priority over killing power.

Trivia

 * The HK21 has a noticeably slower rate of fire in Zombies.
 * The HK21 in Zombies holds 125 rounds, even though it uses the 30 round magazine model instead of the drum magazine. This high magazine capacity was most likely for balancing reasons, as LMGs in Call of Duty: World at War had more than a hundred rounds in Zombies.
 * The HK21 has a fingerprint on the back of the iron sight.
 * When changing the magazine, if one listens closely, removing the magazine uses a similar sound as the PPSH-41 from Call of Duty: World at War.
 * The "115" in 'H115 Oscillator' is a reference to Element 115.
 * Clan Tags are placed on the rear of the iron sights and are completely clear and visible, even when aiming down the iron sights.
 * On the Wii version, the handguard and stock are black, whereas the Xbox, PS3, and PC versions have a tan color.
 * On the Wii version of Call of Duty: Black Ops, the H115 Oscillator сamo will be green.
 * In third person the HK21 has a lot of muzzle flash; however, it is barely noticeable in first person.
 * In the Create-A-Class display, the character's arm goes through a corner of the gun's stock.
 * The iron sights' range are set to '2'.
 * In the trailer for Call of the Dead, the HK21 can be seen with a Drum Mag and an Infrared Scope. However, this setup does not appear in the map.
 * Hudson's HK21 has a drum mag as default during the fight on Rebirth Island.
 * In early stages, the HK21 had an olive finish rather than a tan one.