8.5mm Mars

Cartridge Data Published On: December 20, 2014 at 11:36 pm by Bullet-Blog and last updated on February 12, 2015 at 11:24 am


8.5x26mm Mars, .330 Mars


The 8.5mm Mars (AKA: 8.5x26mm Mars, .330 Mars) is a Center Fire cartridge with a Bullet Diameter of 0.331 in” (8.41mm) that is primarily used in Pistols. The 8.5mm Mars originated in The United Kingdom in 1899. The 8.5mm Mars also has a case length of 1.024 in” (26.01mm) and an overall length of 1.449 in” (36.8mm).


The 8.5mm Mars is the sibling cartridge to the 9mm Mars and was an experimental English pistol cartridge developed around 1899 for use in the Mars Automatic Pistol also known as the Webley-Mars Pistol. The cartridge was created by necking down a .45 Mars Long case to accept the smaller projectile. The 8.5mm Mars was significantly more powerful than many of the other cartridges of its day in terms of both muzzle energy and velocity. Published data sites velocities well over 1500fps with muzzle energies reaching above 700 ft-lbs with a 139-grain projectile, putting it into the range of the more modern .357 Magnum cartridge.

The 8.5mm Mars pistol cartridge closely resembles a larger and fatter version of the 7.62mm Tokarev cartridge, an offshoot of the 7.65mm Borchardt and 7.63mm Mauser cartridges. The cartridge, although being incredibly powerful never saw commercial success and was overshadowed by more popular cartridges of its time, with less than 100 Mars Automatic Pistols ever being manufactured before production ended in less than a decade.

Cartridge Details

  • Year:
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  • Primer:
  • 1899
  • The United Kingdom
  • Rimless, Bottleneck
  • Pistols
  • 0.331 in” (8.41mm)
  • 0.358 in” (9.09mm)
  • 0.417 in” (10.59mm)
  • 0.421 in” (10.69mm)
  • 0.409 in” (10.39mm)
  • 0.04 in” (0.89mm)
  • 1.024 in” (26.01mm)
  • 1.449 in” (36.8mm)
  • Center Fire (Small Pistol)

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