The Armalite/Colt AR-15 series of weapons is a lightweight, air-cooled, magazine fed, autoloading, centerfire rifle, and is probably the most famous assault rifle family ever built by the United States, first appearing in 1958 and continuing to serve 50 years later. The AR-15 is a further development of the AR-10, a 7.62mm rifle developed by Eugene Stoner. The rifle was later adopted by Colt into various successful designs for both the military and civilian markets. Variants have been present in every Grand Theft Auto IIIera game; they are useful in almost any situation, boasting accuracy, power and magazine capacity. Since the rifle fires the relatively powerful 5.56mm NATO round, it has a noticeable recoil force, albeit not nearly as much as the bigger AK-47. Throughout the games, the models of the AR-15 derivatives differ slightly, along with zoom capability, fire-rate, and power.
In Grand Theft Auto III, the firearm is an 'exaggerated' M16A1, with an extremely high rate of fire and a 60 shot magazine. In GTA Vice City, the weapon is rendered more realistically, albeit anachronistically — it resembles an M4 Carbine (specifically, the Colt Model 733 Carbine), which did not exist in 1986, only entering service in 1995.
GTA Vice City Stories (1984): An M16, named "Assault Rifle" in-game. It is chronologically accurate, and its rate of fire is true to real-life M16s. Lance Vance mentions the M4 during a mission, which is an anachronism.
GTA Vice City (1986): A Colt Model 733, incorrectly titled "M4" within the game (the M4 was not introduced until 1995).
GTA San Andreas (1992): A Colt Model 733, again titled "M4" in-game. This version has an unrealistic reload animation wherein CJ charges the weapon with his left hand — real M733s are charged with a rear-mounted handle. This rendition holds a 50 rounds per magazine, not possible with real-life M733s. In the mission Stowaway, a government agent is shown holding a Colt M16A1; this, however, is never available to use in-game.
GTA Liberty City Stories (1998): A Colt Model 733, again titled "M4" in-game. Accurate by timeline and rate of fire. Like the San Andreas rendition, the reload animation is inaccurate.
GTA III (2001): An M16A1. This version is highly inaccurate, with a 60-round magazine and an exceptionally high rate of fire.
GTA IV (2008): An M4A1, titled "Carbine Rifle" in-game, this version is accurate both in timeline and overall features, although it sports a peculiar rear sight design and lacks a carry handle, giving it some resemblance to the similarly-designed Heckler and Koch HK416.
Bedford Point, Staunton Island - In the walled off area in the southeast part of Liberty Tree Offices (use the nearby Moonbeam, park it by the lowest part of the wall, climb the Moonbeam, and jump over the wall to access).
Cedar Grove, Shoreside Vale - On the back porch of the pink house (fourth from the west) at The Homes.
Cochrane Dam, Shoreside Vale - Near the top of the stairs for the west dam platform (not the top of the Cochrane Dam power house) at the base of the Cochrane Dam.
Starfish Island - In the small room at the bottom of the Mansion's stairwell east of the main entrance after the completion of Rub Out.
Downtown - Available to buy from Ammu-Nation after completion of Rub Out ($5,000).
Little Haiti - In the middle of a cluster of shacks in the center of the North Haitian Neighborhood (just south of Auntie Poulet's house).
Little Havana - At the west side of the red and white building directly across the street west of Cafe Robina.
GTA San Andreas
Los Santos International Airport, Los Santos - Next to the runway, there are three white and yellow striped "ramps". Between those which are placed at the end of the runway.
The AR-15 in Grand Theft Auto IV is referenced in-game as the Carbine Rifle. It can be purchased from the back-alley gun shops for $5,000 and each additional magazine will cost $100. It can be purchased from Little Jacob for $3,500 and each additional magazine costs $70. The Carbine Rifle can also be acquired from NOOSE officers and certain LCPD officers.
Algonquin Bridge - Can be found atop the roof of the pedestrian walkway on the Algonquin side, from the monorail station entrance.
Easton - Can be found well-hidden behind some trash cans on the east side of Grand Easton Terminal. The trash cans can be reached quickly through an alley on Jade St.
Leftwood - Can be found underneath the pier where the strip mall is situated off Beaverhead Ave. The strip mall can be seen from the cliff where NikoexecutesAiden O'Malley during the mission Tunnel of Death.
Tudor - Can be found in a small loading dock area on the north side of the old Sprunk factory.
Tudor - Can be found atop the northern superstructure of the old rail bridge that spans the river which divides Tudor and the Acter Industrial Park.