The Mars automatic pistol, also called the Webley-Mars or the Gabbett-Fairfax, is a British semi-automatic pistol.
The gun was designed in 1897 by Hugh Gabbett-Fairfax. It was originally manufactured by Webley & Scott of Webley revolver fame, then by other other small manufacturers. Production was halted in 1907 after only about 80 were made. Originally supposed to be a replacement for the Webley revolver, it was submitted for no less than seven trials, but was rejected every time due to unacceptably high recoil, ridiculous muzzle flash and mechanical complexity.
The gun proved incredibly unpopular with those unfortunate enough to use it: the Captain in charge of tests of the Mars at the Naval Gunnery School in 1902 observed "No one who fired once with the pistol wished to shoot it again." Firing the Mars was described as "singularly unpleasant and alarming".
While Gabbett-Fairfax wanted the guns to be put into service, he did not listen to the complaints and fix the problems with the Mars, causing his company to go bankrupt.
The Mars had an interesting feeding system where it pulled cartridges out of the magazine from the rear and then lifted the up to the breech face, a method of operation that has only ever found a place in later belt-fed machine guns. Whenever it fired, the whole forend would recoil back to cycle the weapon, pushing back on the slide and ejecting the spent casing rearwards.
All examples produced were hand made and hand finished: no two are exactly alike in dimension (a fairly common occurrence prior to the era of mechanized factory production) and some have features others do not.
The Mars accepted 8.5mm Mars, 9mm Mars, .45 Mars Long Case and .45 Mars Short Case; all these cases are bottlenecked with large powder charges, developing muzzle velocities more commonly associated with rifles. The pistols which fired .45 rounds were the most powerful pistols in the world at the time.