Sentry Gun

The Sentry Gun is a fictional weapon, though in principle automated and remote-controlled weapons are used increasingly on battlefields and for high-security installations. It, as well as the UAV and Predator, are indicative of the increasing role of unmanned technology on the battlefield.

Campaign
An M5 Sentry Gun is featured in Call of Duty: Modern Warfare 2 during the level 'Wolverines!'. It is positioned atop Nate's restaurant, where it provides autonomous cover for Sergeant Foley and his team during the recovery of codename "Raptor". Ramirez (the player character) can reposition the sentry gun as needed. An enemy sentry gun is seen in Exodus.

Special Ops
Sentry guns are available for use in Homeland Security, Wardriving and Wreckage. They are especially useful in Homeland Security in helping defend your position, though they'll need to be well protected in order to last through the waves of enemies.

Multiplayer
 is a multiplayer kill streak reward in Call of Duty: Modern Warfare 2. After achieving a 5-kill streak (killing 5 enemy players in a row without dying) or 4 with the hardline perk the player can call in a chopper that drops an automated turret (much like a care package). It can detect enemies at a moderate distance, with its cone of fire centered on where its user positions it. The turret can be picked up and moved; the turret is disabled while held, and the player is unable to use weapons or other equipment.

Any players with the Cold-Blooded perk will not be targeted by the turret. The sentry gun can be disabled with a single melee hit or by gunfire. It can also be avoided by moving around its flank, outside of its firing arc. A riot shield user can approach the sentry gun and knock it down with the shield bump. If approached from behind, it can be disabled with a single melee stroke.

As with all kill streaks you can achieve this kill streak with one less kill using the Hardline perk.

In objective-based games such as Capture the Flag or Sabotage, the Sentry gun can provide invaluable support while protecting a flag or bombsite. Even on Hardcore, the gun can absorb a decent amount of gunfire before being destroyed. However, it can be destroyed by indirect fire through predator missiles or other aerial support weapons.

Sentry Guns can be benifical for snipers for numerous reasons. First, Snipers can only have one claymore to cover them while they snipe. Sentry Guns can provide cover for the sniper rather than a claymore meaning the player does not have to sacrifice a Frag grenade, Throwing Knife, etc for a claymore. Also, unlike claymores where the enemy can come in really close, sentry guns can keep enemies pinned down at a distance and thus, not allowing the enemy to get in close enough to shoot you at an angle or throw a grenade at you.

Note - If you call in 50 sentry guns (in a lifetime, not in a row), you will recieve an animated emblem. It is a sentry gun, rotating left and right and firing.

The same applies to any killstreak-reward challenge.

Tactics

 * A good tactic to level up quickly in multiplayer is to find a person with the sentry gun and with the riot shield armed walk up to the gun and sit there while getting shot at, you will level up roughly about one bar per 3 minutes.
 * It is best that you place a sentry gun with its weak back-side against a wall so that it can't be ambushed.
 * Also, if there are no walls around, place the sentry gun in a corner so that it can get a full 90 degrees of shooting abilities.
 * The best way to approach the Sentry Gun is to use the riot shield and bash the sentry gun.
 * Semtex is very effective at neutralizing Sentry Guns. Usually one well-aimed Semtex will disable it.
 * Having Cold-Blooded will allow you to approach the sentry without it shooting you.
 * When sniping, using Sentry gun to defend your backside and the entrances and claymores will make your "camping" spot fairly safe.
 * Flash bangs and stun grenades seem to disable the gun for a short period of time. Using smoke grenedes allows you to sneak up on it without being detected as easily.

Trivia

 * The original sentry gun concept art used a XM312 machinegun instead of a M134 minigun.
 * In the Museum, you can read the writing on the ammo box for the Sentry gun, which reads: "600 Cartridges// 7.62 IW Sentry // Infinity = M1920" Followed by a serial number. The IW and Infinity is most likely an Easter Egg referring to Infinity Ward, the developers, the infinity could also be a reference to the fact that the sentry gun DOES in fact have infinite ammo even though it says it holds "600 Cartridges".