All of the 101st Airborne soldiers in the film carry XM16-E1 rifles, the interim variant of the M16 rifle which combined the 3 prong flash hider with the A1 style upper receiver. In reality, the 101st AB, at this stage of the war, did NOT carry the XM16-E1, but had the M16A1 with birdcage flash hider, a fact pointed out by Hamburger Hill Veterans when the film was released.
MGC Replica M16
Soldiers in the beginning of the film have ModelGun Corp replica MGC M16s slung to their backs as they load wounded onto helicopters. One of the giveaways is the 'blued' 20 round magazine (the real 20 round magazine is anodyzed aluminum), the shape of the pistol grip and the rear sling swivel. The most obvious detail is not seen here, the fake forward assist of the replica rifle.
AK-47
Chinese Type 56 Assault Rifle
Other than the milled receiver AK-47s (which are probably Poly-Technology Legend series rifles), there are obvious stamped receiver Type 56 style AK rifles with underfolder spike bayonets (aka "PigSticker")
M60
M60D
The D Model of the M60 is seen on all helicopters in the film.
SKS/Type 56 Carbine
The Chinese variant of the Russian SKS, the Type 56 Carbine with spike bayonet, is used by the NVA combatants in the film.
M79 grenade launcher
Used by McDaniel (Don James) and then later by Pvt. Joe Beletsky (Tim Quill)
M26 grenade
A variety of 'lemon grenades' are seen on soldier's web gear throughout the film. They are often seen from a distance on webbing or in men's hands as they are thrown. In real life they are supposed to be M61 Grenades (virtually identical to the M26A1 lemon grenades most associated with Vietnam), however, these have a slightly unusual shape, implying that they are some sort of 'trainer' grenade that is not often used to impersonate the M26/M61 series of grenades.
Fake RPG Training Aid
When Sgt. Frantz (Dylan McDermott) is lecturing the new members of the platoon, he uses a former NVA crossover (a participant in the Chu Hoi program) named "Han" to demonstrate how 'not paying attention' will get them killed. Han is 'armed' with a long empty tube made to resemble an RPG launcher of sorts. It has a dud Warhead on it. "Han" demonstrates his skill and ability by avoiding the noisemakers, trip wire and barbed wire of the perimeter to get within striking distance of the G.I.s
Chinese Type 58 Stick Grenade
Throughout the film, the enemy uses the Chinese Type 56 (aka Type I) stick grenade. It is an oval pineapple style grenade on a short wooden stick and noticeably shorter than the famous German Stielhandgranate of WW2 fame.
Browning M2HB Machine gun
Seen in the distance on some of the perimeter shots of the base camps and mounted on M113 APCs.