The design for the Desert Eagle was initiated by Bernard C. White of Magnum Research and Arnolds Streinbergs of Riga Arms Institute, who filed a US patent application for a mechanism for a gas-actuated pistol in January 1983. This established the basic layout of the Desert Eagle. A second patent application was filed in December 1985, after the basic design had been refined by IMI Systems (Israel Military Industries) for production, and this is the form that went into production.
The pistol is fired by a single action hammer, and has a manual safety switch on the slide. The ambidextrous safety switch rotates a drum mechanism which sits over the firing pin, causing the firing pin to lock in, which prevents it from moving forward and reduces the possibility of the gun discharging accidentally. With the safety off, pulling the trigger releases the hammer to fall downward, hitting the firing pin and causing the chambered round to discharge.
The Desert Eagle uses a gas-operated mechanism normally found in rifles, as opposed to the short recoil or blow-back designs most commonly seen in semi-automatic pistols. When a round is fired, gases are ported out through a small hole in the barrel in front of the chamber. These travel forward, through a small tube under the barrel, to a cylinder underneath the front of the barrel. The slide, which acts as the bolt carrier, has a small piston on the front that fits into this cylinder. When the gases reach the cylinder, the piston pushes the slide rearward, with a large pin inside the camming surface in the rear of the bolt causing the bolt to rotate and unlock. A mechanism on the left side of the bolt prevents the bolt from rotating freely as the slide moves, forcing it to remain aligned correctly with the barrel while the breech is open. The spring loaded ejector is continually being depressed by the case, until the case is free of the chamber and the tension from the ejector is released, causing the case to eject, breaking free of the extractor in the process. The slide reaches its rearmost position, then moves forward again under tension of the recoil springs. The bottom lug of the bolt pushes a new round into the chamber, then the bolt locks up and the gun can be fired again.
The rotating bolt has four radial locking lugs, with the extractor on the right hand side fitting where the fifth lug would be, and strongly resembles the 7-lug bolt of the M16 series of rifles, while the fixed gas cylinder/moving piston resemble those of the Ruger Mini-14 carbine (the original patent used a captive piston similar to the M14 rifle).
The advantage of the gas operation is that it allows the use of far more powerful cartridges than traditional semi-automatic pistol designs. Thus it allows the Desert Eagle to compete in an area that had previously been dominated by magnum revolvers. Downsides of the gas-operated mechanism are the large size of the Desert Eagle, and the fact that it discourages the use of unjacketed lead bullets, as lead particles sheared off during firing could clog the gas release tap, preventing proper function.
Switching a Desert Eagle to another chambering requires only that the correct barrel, bolt assembly, and magazine be installed. Thus, a conversion to fire the other cartridges can be quickly accomplished. The rim diameter of the .50 AE (Action Express) is the same as the .44 Remington Magnum cartridge, consequently only a barrel and magazine change is required to convert a .44 Desert Eagle to the larger, more powerful .50 AE round. The most popular barrel length is 6 in (152 mm), although a 10 in (254 mm) barrel is available. The Mark XIX barrels are machined with integral scope mounting bases, simplifying the process of adding a pistol scope.
The Desert Eagle is fed with a detachable magazine. Magazine capacity is 9 rounds in .357 Magnum, 8 rounds in .44 Magnum, and 7 rounds in .50 Action Express. The Desert Eagle’s barrel features polygonal rifling. The pistol is primarily used for hunting, target shooting, and silhouette shooting.