[LINK] Mischa & Kitsune
The Mateba Model 6 Unica (aka the Mateba Autorevolver), made in Italy, is the only semi-automatic revolver currently in production [IF it is still in production -- see footnote]. After the first shot is fired DA style, the chamber is automatically rotated and the hammer is cocked, ready for firing with a light SA trigger pull (see extension for details on how this is done).
The Unica is chambered for the .357 Magnum cartridge (38 specials don't produce enough recoil to operate it reliably). It also be ordered in 44 Magnum (and possibly 454 Casull). The recoil powered mechanism reduces felt recoil considerably. The tendency to rise is reduced by the fact the barrel is aligned with the bottom of the cylinder.
A 500 S&W version (as suggested in a comment to an earlier A-C-E post by Chad) would be awesome. It would also be rather large and heavy (the .357 version weighs almost 3 lbs empty), which would also reduce felt recoil.
Better yet, a Mateba Griffone carbine (with 18 in. barrel, forearm, and overfolding stock) in 500 S&W, or 50 Alaskan.
According to several message board posts (not yet confirmed) Mateba now makes only M1911 clones. If this is true, the Mateba autorevolver had a short life span, since it was first produced in 1997. Used ones occasionally pop up on auction boards. Parts and repair might be an issue.
S&W should commission Mateba to build a 500 S&W autorevolver exclusively for S&W. Then, S&W could claim to sell the only semiauto revolver.
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Note the barrel aligns with the bottom of the cylinder, reducing muzzle rise.
Mateba semi auto operation:
The first trigger pull is a normal double action pull, like most revolvers (unless one pulls the hammer back manually). It cocks the hammer, and then releases it, firing the gun. Upon firing the upper part of the frame recoils. This movement then cocks the hammer, and automatically rotates the cylinder. When the upper frame has completely recoiled, it is pushed forward again by a spring. When it has returned to its forward position the gun is ready to fire another shot, only this time a light pull in Single-Action mode, as the hammer is already cocked and the cylinder rotated.
The Webley-Fosbery (details), first produced in 1901, was also semi-automatic [I don't call something automatic unless it fires multiple rounds with one pull of the trigger], but has been out of production since just before WWI.