The XM16E1 assault rifle are used by the soldiers of the 1st Cavalry Division including Lt. Colonel Hal Moore(Mel Gibson). Later on the film during the Ia Drang battle Joe Galloway (Barry Pepper) uses one as well. These were actual XM16E1's used on the film for the heroes.
M1 Carbine
A Korean war era M1 Carbine is carried by the South Vietnamese (ARVN) advisor dressed in Tigerstripe fatigues. He appears in the scene in which the NVA scout is caught and interrogated. Viet Minh soldiers also use them against the french during the intro.
M60 machine gun
The M60 machine gun is are used by US soldiers. Various Door gunners use them as well.
Colt M1911 pistol
A Colt M1911 is fired by Sgt. Maj. Basil Plumley (Sam Elliott) during a close combat sequence and is also seen in the holsters of his fellow soldiers.
I read somewhere (I think LMO) that Sam Elliot used an older M1911 not an A1. Gibson on the other hand did use an A1. I'm sure Steve would know something about it, since he worked on the film. - Gunmaster45
Sam Elliot did indeed used a Colt 1911 rebuilt for World War II and Mel Gibson used a Colt 1911A1 pre-war commercial issued to the military during World War II. -Steve
Colt M1911A1 pistol
A Colt M1911A1 is seen in the holster of Lt. Col. Hal Moore (Mel Gibson) during a close combat sequence, shooting an NVA soldier attempting to bayonet him while he's on the radio.
M26 Hand Grenades
In several scenes, U.S. soldiers can be seen with M26 hand grenades strapped to their pouches.
PPSh-41
The NVA and the Vietcong use PPSh-41s submachine guns during the intro sequence and the rest of the movie.
Genuine AK-47s
During the movie the North Vietnamise Army (NVA) use Genuine AK-47s with Milled Receivers.
In the opening scene where the french soldiers are ambushed during the Indochina War, various french soldiers use MAS-36 rifles.
Smith & Wesson M-13 Aircrewman
The .38 caliber revolver pulled out by Maj. Bruce "Snake S!@#" Crandall (Greg Kinnear) is most likely a Smith & Wesson M-13 Aircrewman, an unsuccessful lightweight aluminium-cylindered revolver designed for US military flyers.
GE M134 Minigun
A pair each of GE M134 Miniguns are seen mounted on the gunship Hueys at the climax of the film, and one is also on display on a table in the beginning of the movie.
M1928A1 Thompson
As the American soldiers are heading off for battle you can see a South Vietnamese soldier holding up an M1928A1 Thompson with a 20-round magazine.
Browning M1919A4
Two Browning M1919A4s can be seen mounted on French jeeps on the intro sequence.
MAT-49
Various French Soldiers use MAT-49 submachine guns during the opening Scene. Various North Vietnam soldiers and Vietcong soldiers use them as well during the Battle of Ia Drang.
RPG-2
A NVA soldier wearing a gas mask uses a RPG-2 to kill american soldiers.