All of the vehicles in the movie are Mercedes Benz. The C Class cars came out in 2015, and the G550 and GL SUV came out in 2013. The only car that was around in 2012 was the M Class SUV used in multiple scenes.
According to IMFDB.org, the Salient Arms International Tier One AR-15 'GRY' rifle used by the GRS operatives in the film has only been available since 2015, while the events of the film occurred in late 2012.
About 36 minutes in, one character video-calls his family from a Galaxy S5 smartphone. That model was released in 2014, 18 months after the events depicted in the film. As the scene cuts to another angle, the phone changes to a Blackberry, which doesn't have a front-facing camera.
During the second attack on the Annex, Rone shifts his M240B machine gun to engage targets coming from 'Zombieland'. When he sets it down and starts to fire it again, however, it has the sound of the M249 SAW light machine guns used by Tanto and Tig.
The flight into Benghazi at the beginning of the film depicts the aircraft as belonging to at least 2 different airlines: Air Afrique (interior of aircraft), Ryanair (aircraft in final approach before touchdown) and a third one (when passengers were walking to the terminal, aircraft in background).
At the beginning, a Land Rover travels down a road with all of the buildings on the right side of the vehicle in a wide shot. In the next shot, inside the vehicle, buildings are on both sides. In the next shot, buildings are on the left side of the vehicle. In the last wide shot of the Land Rover traveling down the road, all of the buildings on the right again.
Over the several times the CIA Annex is attacked, despite the grievous casualties inflicted on them, there are few bodies of the attackers seen on the ground during the subsequent attacks. Granted, many of them fell in areas with long grass that would obscure the bodies, and bodies are seen definitively after the attack when the attackers' families recover them. However, there still should have been more bodies visible during the attack scenes.
After the team meets up with Alec at his security room and is shown collecting hard drives, Tanto tells a panicking Amahl to get it together and stop pointing his gun at him. Amahl's glasses go from in his hand, to on his face, and then back to his hand as the camera's POV changes.
At around 37:31 minutes, the Mac Book Pro Retina Kris 'Tanto' Paronto put on the table indicates OS X Yosemite system. However in 2012, when the movie took place, neither the Mac Book Pro Retina nor the OS X Yosemite was introduced yet.
A distinctive prop M16A2 rifle, almost certainly a rubber stunt replica, with a damaged carry handle appears twice on the film in the hands of two very dissimilar people and situations. The first time it is seen is in an arms bazaar, when Rone brushes away a vendor trying to sell him RPG warheads; the rifle is being held by a man in a white shirt towards the left side of the frame in the background. The second time is when the U.S. Army's 10th Special Forces Group is mobilizing; what appears to be the same rifle, with the distinctive bent carry handle, is now being used by a U.S. Army Special Forces soldier.
Libya's official language is Arabic. When Jack Silva arrives at the airport, a terminal announcement is in Persian. When an embassy staff try to open Safe Haven during the attack, the attackers are speaking Persian.
In several scenes, the distinctive domes and towers of Maltese baroque churches can be seen in the background. Libya does not have that type of church. A Maltese flag is briefly visible as the ambassador's motorcade drives past.
When the men and women from the compound board the private jet at what appears to be an airplane graveyard, one aircraft's serial number starts with "N," which means it's registered in the US. Why would an airplane graveyard full of US licensed commercial aircraft from a bygone era (propeller driven commercial aviation) be in Libya?
Sean Smith is briefly seen playing on an Xbox console the night of the attack and holding a controller when he meets up with Ambassador Stevens and Agent Wickland. In reality, he was on a computer playing an online RPG game, EVE Online, with friends. One friend confirmed in his eulogy that Smith, over voice chat, shouted about gunfire then promptly logged out of the game and never returned.
Some of the Ops-Core FAST helmets worn by both the CIA GRS operators and U.S. Army Special Forces soldiers seem to be non-ballistic versions that almost certainly would not be used in combat situations.
The film claims that the military refused to provide air support during the attack. In real life, multiple Senate investigations found that the planes in nearby Italy were not combat-ready. The nearest combat capable craft were stationed in Djibouti, on the other side of the continent.
The militants pour what is said to be diesel fuel throughout the compound, then lighting the fuel with a lighter. Diesel is very hard to light with an open flame, and when lit will burn slowly. In all likelihood, the diesel would have actually put the lighter out and would not have created the near-instant billowing smoke shown in the movie.
During one attack against the CIA annex, Bob, the CIA station head, radios the GRS operators that '17 Feb says you're firing at them!', and Tanto answers 'Somebody started shooting at us first!" The first shot in this attack was fired by GRS sniper 'Boon', in response to an attacker throwing a bomb at the annex.
According to the book, DS Agent Wickland used an M4 carbine when he was with the Ambassador and Sean Smith, while Agent Henderson had a shotgun. In the film, Wickland uses the shotgun and Henderson has an MK.18 carbine, a shortened M4.
In the film's depiction of the 2012 Benghazi attacks, Rone is first wearing an orange plaid shirt, before switching to a greenish-grey one towards the end of the film. However, in the book that the film is based on, Rone apparently wore the orange shirt for the entire time.
When a door of one of the supposedly 'armored' Mercedes Benz vehicles is shut, it looks and sounds like a normal door closing. Armored doors are much heavier (thick bulletproof glass, added Kevlar and other features) than regular doors, and look and sound different when being closed.
The film's characters keep referring to the GRS operators who were formerly U.S. Marines as 'ex-Marines.' There is no such thing. Marines that are no longer active are referred to correctly as 'Marines,' or possibly 'former Marines' or 'retired Marines' but *never* as 'ex-Marines;' some even take the latter as an insult as it implies a dishonorable discharge.
When the men call their families, it's daylight in both places. According to the movie, it was 6:15pm Benghazi time. With a 9-hour time difference between Libya and the west coast of the U.S,. it would be daylight in both locations. Even if the soldiers were 11 hours ahead, as some claim, it would be 7:15am in Los Angeles, well after sunrise in early September.
In several scenes, 40mm grenades change trajectory rapidly, rising in an arc, then suddenly plummeting toward a target. A grenade launcher is an indirect fire weapon, but the 40mm grenade carries a propellant Hi-low system.
When Tig fires a 40mm grenade at the pickup truck with the heavy machine gun, the front end of the truck starts lifting off of the ground a split second before the explosion. The truck wouldn't come up like that without bouncing on the suspension first anyway, given that the grenade hit the hood/grill, not under the vehicle.
Libya drives on the right. While all the key vehicles were left-hand drive with Libyan plates, the buses and Bedford 4-tonner are right-hand drive, and the Bedford has a Maltese number plate. The high-speed convoy at 31:30 drives on the left, as is the rule in Malta.
When the attackers take the ambassador's house, the American crew locks themselves in the safe room. When the attackers kick the door and also try to shoot it open, the key is hanging on the lock. The bronze label is hanging there.