HK21

The HK21 is a light machine gun featured in Call of Duty: Black Ops.

Multiplayer
The HK21 is a fully automatic light machine gun with moderate recoil, moderate rate of fire and a 30 round magazine. It is available at Level 2 to the player, as part of the LMG default class.

The HK21 will kill in 3 shots at any range, or 2 headshots, and has medium recoil. This makes the HK21 extremely powerful at medium range. Long-range encounters can be dealt with by firing single shots. The HK21 is tied with the Stoner63 for the smallest capacity out of all the LMGs so the round drum 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 this reason, the Red Dot sight or Reflex Sight is recommended.

Although the HK21 has very low movement speed, perks like Lightweight are not recommended. Machine guns like the HK21 are better suited to large amounts of stationary fire, particularly when defending or supporting objectives. For this reason, Scavenger is recommended to keep supplied with ammo. Steady Aim benefits the HK21 as it improves its CQB capabilities. 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, but you should be able to kill all enemies and get to cover without needing to reload. Hardened or Warlord along with extended mags can be more useful than Sleight of Hand. Since this weapon is best used stationary, perks that affect movement are not recommended. Ninja and Marathon for example, don't play to this weapon's strengths. Hacker or Tactical Mask is recommended instead. Hacker will let you move into position without falling into a trap by equipment, and tactical mask pro will prevent enemies from using most tactical grenades to stun you, making defending and supporting much easier.

When using machine guns like this, it is important to remember that they are NOT assault rifles. Do not attempt to use them as such. Use your high firepower to support the team. Don't try and rush the enemy, as you are too slow to do damage and it's easier to use a SMG or assault rifle, than it is to waste perks trying to turn the LMGs into something they aren't.

Attachments

 * Infrared Scope
 * Red Dot Sight
 * Extended Mag
 * ACOG Scope
 * Reflex thumb|300px|right|HK21 Attachment Overview

Zombies
The HK21 can be found in the Zombies game mode and is only obtained from the mystery box. It starts with a magazine size of 125 rounds and with a extra 500 rounds, therefore making it and the RPK the replacements for the MG42 and Browning M1919 in the Black Ops Zombies mode. When Pack-A-Punched, it becomes the 'H115 Oscillator'. This adds twenty-five rounds to the magazine while increasing ammo capacity along with the usual additions. The H115 Oscillator may also be a reference to Element 115.

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. The low rate of fire also makes Double Tap Root Beer beneficial, but not a necessity. However, it may be wise to switch to a weapon with more mobility if fleeing becomes necessary, as the HK21 slows movement speed significantly.

Trivia

 * In Zombies, the HK21 has a noticeably slower rate of fire.
 * The sound effect played when the player picks up the HK21 and works the action is shared with the Barrett .50cal and the Tactical Insertion.
 * This weapon is very similar in appearance to the PSG1 because they are both based off the G3 rifle - the PSG1 is a sniper rifle variant and the HK21 is an LMG variant.
 * The HK21 in Zombies holds 125 rounds even though it uses the 30 round magazine model. The weapon would have to be used in the belt-fed configuration in order to hold this much ammunition.
 * It has a finger print on the back of the iron sight