Mateba Autorevolver

The Mateba Model 6 Unica (often known simply as the Mateba or the Mateba Autorevolver) is a recoil operated semi-automatic revolver, one of only a few of this type ever produced. It was developed by Mateba, based in Pavia, Italy. Inventor Emilio Ghisoni (1937-2008), who was also famous for later designing the Chiappa Rhino, is listed as the owner of which details the operation of the weapon.
As of 23 March 2018, Mateba (now based in Montebelluna, Italy) has reintroduced the 6 Unica and Grifone Carbine. Mateba is making the Unica in .357 Magnum and .44 Magnum calibers only.
Design.
The Mateba Model 6 uses the recoil from firing to rotate the cylinder and cock the hammer, unlike conventional revolvers, which depend on the user physically pulling the trigger and/or cocking the hammer to actuate the weapon's mechanism of operation.
The Mateba Autorevolver's barrel alignment is different from most other revolvers. The barrel is aligned with the bottom of the cylinder instead of the top. This lowers the bore axis (line of the barrel) which directs the recoil in line with the shooter's hand thereby reducing the twisting motion or muzzle flip of normal revolvers.
The gun's entire upper assembly (barrel, cylinder and frame) are mounted on rails on the lower frame, which houses the trigger, hammer, and grip, and recoils 1/2 of an inch, or 12.7mm, on firing. The rearward motion of the upper assembly cocks the hammer, and the cylinder is rotated on the forward stroke. This unique action makes this revolver a semi automatic weapon, making it one of the very few semi automatic revolver designs, another notable design being the Webley–Fosbery Self-Cocking Automatic Revolver. The inclusion of the 454 Casull chambering makes the gun one of, if not the, most powerful semi-automatic handgun ever produced. This chambering places the Mateba in comparison to firearms like the Wildey pistol chambered in .475 Wildey Magnum and .44 Mag examples of the AutoMag pistol.
Variants.
The following are variants of the Mateba revolver:
In addition, their barrels can be changed with interchangeable 3", 4", 5", 6", 7" and 8" inch barrels.
Mateba Grifone.
Also available was the Mateba Grifone, a revolver carbine which mated an barrel, handguard and buttstock to the Autorevolver's frame and action. It was available in .357 Magnum and .44 Magnum. A version in .454 Casull was available which also allowed .45 Colt ammunition to be fired.
Multiple cartridge capability.
Mateba Autorevolvers chambered in .357 Magnum can be loaded with .38 Special ammunition. Typical .38 Special loads do not have enough power to fully cycle the recoil mechanism, but the weapon will still function with a double-action trigger pull. There are two optional recoil springs designed specifically for .38 Special cartridges that can be installed by the operator to overcome this problem (.38 Special and .38 wadcutter). Replacing the spring requires the removal of the slide assembly, which is blocked by a retaining pin held in place by a small set screw in the triggerguard. The barrel shroud acts as the spring keeper and guide rod bushing.
Autorevolvers chambered in 44 Magnum can have the recoil spring swapped out to shoot 44 special and 454 Casull can fire 45 Long Colt with a spring swap.