Dirty Harry is the 1971 crime film that introduced the character of "Dirty Harry" Callahan to movie audiences. Clint Eastwood stars as SFPD Inspector Callahan, who is assigned to head up the investigation to catch a serial killer who calls himself "Scorpio" and who threatens to kill a citizen of the city each day until his ransom demands are met. Dirty Harry was the first in the film franchise and introduced the now iconic .44 Magnum Smith & Wesson Model 29.
The following weapons were used in the film Dirty Harry:
Smith & Wesson Model 29
The now iconic revolver carried by Inspector "Dirty" Harry Callahan (Clint Eastwood) in the film is a Smith & Wesson Model 29, chambered in .44 Magnum. As the script originally called for a Smith & Wesson Model 29 with a 4" barrel, this eventually proved troublesome for the filmmakers, since the Model 29 was no longer in production at the time. Before shooting began, Eastwood contacted Bob Sauer (then a representative for Smith & Wesson) to acquire the gun for the film. It was a challenge, but Fred Miller at the plant had a couple assembled from parts eventually. To better familiarize himself with the weapon's handling and recoil, Eastwood took one to a gun range and fired live rounds through it. Unlike the gun in the script, the only barrels acquired for the guns in this film were the 8 3/8" barrel and the 6 1/2" barrel. Both can be seen used in some scenes. The blanks it fired were custom made since the 5-in-1 blank didn't fit the chambers. It is said scriptwriter John Milius was presented with one of the actual guns used in the film as a gift later on.
As for Harry's line in the film about the .44 Magnum being "the most powerful handgun in the world", one should note that even in the 1970s, the .44 Remington Magnum cartridge had been eclipsed in size and power by the .454 Casull round, however, the first widely available commercially sold revolver chambered for the .454 Casull would not come for another ten years, so his statement for the time frame is accurate.
Winchester Model 70
A Winchester Model 70 chambered in .458 Winchester Magnum is used by Insp. "Dirty" Harry Callahan (Clint Eastwood) in a failed attempt to kill the Scorpio Killer (Andrew Robinson) on the rooftops over looking the church. The .458's parabolic trajectory and immense recoil would make it an exceedingly poor choice for use as a long distance counter-sniper rifle, but it is consistent with Callahan's preference for massive overkill.
Winchester Model 12
The Bank Robber at the start of the film, being played by Albert Popwell (who would play four separate roles in the Dirty Harry series) wounds Insp. Callahan (Clint Eastwood) with a shot from his Winchester Model 12, but is disarmed during the famous "Do I feel lucky?" scene.
Colt Detective Special
The Scorpio Killer (Andrew Robinson) carries an MP40 submachine gun in the same rifle case as his sniper rifle, along with some spare magazines. He uses it to shoot at Insp. Callahan (Clint Eastwood) and Insp. Chico Gonzalez (Reni Santoni) during the shootout on the rooftops. Later he fires it at Insp. Gonzales during the fight at the base of the Mt. Davidson Cross.
The Liquor Store Owner (James Nolan) shows the Scorpio Killer (Andrew Robinson) his Walther P38 pistol, which he brags he used to stop several attempted robberies. Unfortunately for him Scorpio hits him with a liquor bottle and takes the gun from him, and carries it up to the climax of the film.
7.7mm Arisaka Type 2 Paratrooper Takedown rifle
The Scorpio Killer (Andrew Robinson) uses an 7.7mm Arisaka Type 02 Paratrooper Takedown rifle as his weapon of choice to kill random people in San Francisco. The rifle is fitted with a Hiram Maxim 1900's style suppressor, and rechambered in .30-06. The rifle is also placed in a sporting style stock.
(Note: Many Arisaka Battle rifles were 'sporterized' in the decades after World War II. For several decades after WW2, the Arisaka rifle was cheap and had no collector value. The value of the Imperial weapons skyrocketed in the 1990s. It is ironic that someone sporterized a 7.7mm paratrooper take down rifle, since now it is one of the rarest and most valuable battle rifles of World War II. An unmodified version is worth thousands of dollars. The sporterized version as seen in the movie is relatively worthless from a collector standpoint).
Evidence: the spent rifle round
One of the robbers during the opening scene tries to shoot at Insp. Callahan (Clint Eastwood) with an unknown snub nose but is ultimately added to his body count.
Unknown Service Revolver
Police patrolling the rooftops for the Scorpio Killer (Andrew Robinson) are seen with unknown revolvers in their holsters.
These are likely either Colt Pythons or Colt Troopers as SFPD officers used both during the period and both are seen being used by SFPD officers in the following films, particularly Pythons in the next film, Magnum Force.