Tugg Speedman (Ben Stiller), along with various other characters, uses a 16" barreled AR-15 Sporter II Carbine throughout the film, which is anachronistic for Vietnam . The original AR-15 Carbine was an SP1 (sold between 1978-1985)), so there was no forward Assist on the upper receiver. Stiller's gun is the A1 version, or what Colt called the "Sporter II version" in U.S. sales. The Colt Model 653 based weapons came after 1973. He should be using an XM177 variation to be accurate to the era. It may be an homage to the movie Platoon since the characters of Barnes (Tom Berenger) and Elias (Willem Dafoe) used the Phillipine export Colt Model 653 rifles. This film uses what is available in the United States, which happens to be the Sporter II carbine, since most of the movie was filmed in Los Angeles and Hawaii.
Kevin Sandusky (Jay Baruchel) and Alpo Chino (Branon T. Jackson) both carry M16A1 rifles fitted with the older style M16 muzzle flash reducers throughout the film.
Jeff "Fats" Portnoy (Jack Black) wields an M60 Machine Gun as his weapon in the film. Jack Black commented on how he got stuck with the M60, which he knew was nicknamed "The Pig", and was tolds he was a natural with it, something he found disturbing. Some other random soldiers are also seen firing M60s during the opening scene.
One of the Guerillas is seen holding a Colt Gold Cup National Match 1911 pistol on Cody (Danny R. McBride) when he flies a chopper to their Heroin base and Portnoy is seen armed with it before Tran kicks it out of his hand, implying it is a rubber prop.
Lazarus is seen using an M1911A1 as his sidearm in the film and uses it several times. Portnoy later gets his hands on it and uses it to hold Tran (Brandon Soo Hoo) hostage.
A door-gunner is seen manning an M60D machine gun during the opening "Hot LZ" scene. The M60D was used during the Vietnam War so it fits the era the film was set.
Speedman and Portnoy are seen with M67 hand grenades attached to their belts and jackets. Since their film is supposed to take place in 1969, it makes sense to see them with these grenades, since '69 was when the M67 began to mass replace the M26 grenade.
M67 hand grenade.Error creating thumbnail: File missingSpeedman keeps an M67 grenade hanging from his jacket.Error creating thumbnail: File missingSpeedman pulls the pin on his M67 grenade to throw at the enemy Guerrilas, and despite it being a dummy grenade, Cody happens to set off some C4 at the same time. Pulling the pin on a grenade like this would cause severe dental damage in real life. Seriously, this film they are making is in serious need of a military advisor!Error creating thumbnail: File missingPortnoy keeps an M67 on his belt.
During the opening "Hot LZ" scene, a Vietnamese soldier tries to throw a Model 24 Stielhandgranate at the Huey chopper as it takes off, so Speedman jumps up and stops the grenade, loosing his hands in the process.
Vietnamese soldiers are seen armed with AKM rifles during the opening "Hot LZ" scene, one of which most notabley dissembowels Sandsuky with his bayonet. It would be more accurate for the Vietnamese to use Norinco Type 56 rifles, the chinese model of the AK. Later the Guerilla soldiers can be seen armed with AKM rifles, which appear to be Egyptian Maadi ARM rifles, one of the most common AKMs used in films.
Several Guerillas, including Tran (Brandon Soo Hoo) are armed with AKMSU assualt carbines modifed with Krinkov parts kits with side-folding stocks to resemble AKS-74U carbines.
Cody keeps a portable Flamethrower among his pyrotechinical gear. When he and Four Leaf Tayback (Nick Nolte) try to escape from the Guerilla's heroin base, Cody give Tayback the Flamethrower, which he uses to hold back the enemies.
Three types of M4A1 carbines are seen used by the Guerilla forces, one of which is seen with the carry handle removed, Knights Armament RIS rails affixed (with no rail covers) and fitted with a Aimpoint red-dot sight, the other with the carry handle attached with an ACOG scope mounted on it. Lazarus grabs one of these rifles and is seen using it when searching for Speedman in the huts, however his does not have the ACOG sight.
One of the Guerillas is seen armed with an CAR-15 rifle with an A2 reciever, ACOG scope, and a 10" barrel, make unknown. Since the 733 has an 11.5" barrel, this is ruled out.
Tran uses a Norinco Type 69 RPG launcher to take out the truck the gang tries to escape in and tries to shoot down their chopper as they escape, the rocket being stopped only by a perfectly thrown TiVo box from Speedman's agent, Rick "Pecker" Peck (Matthew McConaughey).
