Many of the soldiers in the film are armed with M1A1 Thompson submachine guns noted by their triangular "bunny ear" sight housing including Pvt. Kelly (Clint Eastwood) and Master Sgt. "Big" Joe (Telly Savalas). These guns were specially requested by Kelly for his special squad to find the gold behind enemy lines, which is why they are not armed mainly with M1 Garand rifles like a normal squad. Throughout the film, the M1A1 Thompsons sometimes switch with older M1 Thompson submachine guns with more complex bolts and cheaper bolted peep sights on the back with no protective housings.
The older M1 Thompson submachine guns are seen in the hands of many soldiers, which had more complex bolts and cheaper style peep sights which have no protective housings like the M1A1s. They are mainly seen switching with the M1A1s throughout the film as a continuity error.
Pvt. Fisher (Dick Balduzzi) uses an M1 Carbine which he usually keeps fitted with a rifle grenade launcher fixed on the barrel as his main weapon throughout the film.
Despite the fact that the M1 Garand rifle was the most commonly employed weapon in the U.S. Army during WWII, the rifle is seldom seen and is never used or fired in the film. Many are seen slung on the backs of extras as they march past Kelly in his jeep when he talks with Big Joe.
The Belgian FN BAR Type D light machine gun takes the place of the American Browning BAR for the film with noticable differences such as a larger wooden forend, a removable barrel, cooling barrel fins, a pistol grip, and a dust cover which were added to the gun by the Belgian army for it to meet their military requirments. It is most notabley seen in the hands of Pvt. Petuko (Perry Lopez), Pvt. Mitchell (Fred Pearlman) and Pvt. Grace (Michael Clark).
Seen pintle-mounted on the U.S. Sherman tanks under Sgt. Oddball's (Donald Sutherland) command are Browning M1917 water-cooled machine guns, which one tank operator is seen firing at German infantry from inside the tank.
The anti-aircraft version of the Browning M2, the M3, is seen mounted on top of the Sherman tanks under Sgt. Oddball's (Donald Sutherland) command, noted by their perforated barrel shrouds. During the assault on the town, Pvt. Kelly (Clint Eastwood) mans the M3 mounted on Oddball's tank and fires it at a Tiger Tank before the Sherman destroys it with a shot to the weak rear end. The guns appear to be fitted with a muzzle blank adapter which dimensions are clearly smaller than a .50 caliber to allow enough pressure to cycle the gun, though the blanks being fired are indeed .50 BMG blanks.
The Browning M2 M1919A4 machine gun is seen as one of the weapons carried by Kelly's squad and when their vehicles are destroyed by friendly plane fire, SSgt. Crapgame (Don Rickles) is ordered by MSgt. Big Joe to lug the .30 cal around, which he hates and throughout the film he tries to pawn the gun off on others to carry. Like the M3, the 1919 guns in the film are fitted with muzzle blank adapters, more notable on the .30 cals because the muzzles would normally recoil on the real gun but the adapters clearly block them from sight.
Mk 2 Hand Grenades are standard issue with the U.S. Army and all the members of Kelly's squad use them, most notabley MSgt. Big Joe a few times in the film.
Taking place of the M1911A1 handgun, which was likely still in use during the Vietnam war at the time, is the Polish Radom Model 35 pistol which bears resemblance to the 1911 pistol but is clearly different.
Pvt. Gutowski (Richard Davalos), the squad sniper, is armed with a Mosin Nagant M91/30 sniper rifle outfitted with a 3.5PU scope. It is a major innaccuracy for him to be using the Russian sniper rifle as the U.S. wasn't ever on Russian soil during WWII, so aquiring this rifle would be immpossible (there's a good possibility that Gutowski captured the rifle from a German sniper, who originally captured the rifle from a Red Army sniper on the Eastern Front. According to Capt. Clifford Shore, the author of With British Snipers to the Reich, many German snipers were using captured Soviet-made Mosin-Nagant sniper rifles alongside the Mauser Kar98k sniper rifle in Western Europe during the later years of World War II). It would be far more accurate if he had been using a Springfield 1903A4 sniper rifle.
The Karabiner 98k was the standard rifle of the German army during WWII but like many old WWII movies, the MP40 is shown as the main weapon of the Germans (see also Where Eagles Dare), which was the exact opposite in real life. In this film, the Kar98k is actually seldom seen.
Four barreled AA/AT (anti-aircraft/anti-tank) Flakvierling 38s are seen used by the Germans when Oddball and his tanks assualt the train station and they are all destroyed before they inflict any damage on the tanks.
Oddball (Donald Sutherland) keeps a Luger P08 pistol as his sidearm of choice, which somehow seems to fit his quirky character. Instead of keeping it in a Luger holster, he keeps it in the poorly fit U.S. 1911 holster.
In one scene, a U.S. soldier can be briefly seen in the background with a Lee-Enfield No.4 rifle slung over his shoulder - which is odd to see because the Lee-Enfield No.4 rifle was the standard-issue rifle of the British Army and British Commonwealth forces serving in Western Europe during World War II. It is more than likely that the No.4 rifle would have been used as a "stand-in" weapon for either the M1 Garand or the Springfield 1903. A Lee-Enfield No.4 rifle was also seen slung over the shoulder of an American soldier at the US general's headquarters, which gives more evidence that the No.4 rifle was used as a "stand-in" for the Garand and the Springfield by the production crew.
