.45 Mars Long

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.45 Mars Long
Place of originUnited Kingdom
Production history
Case typeRimless, straight
Bullet diameter11.40 mm (0.449 in)
Neck diameter12.06 mm (0.475 in)
Shoulder diameter12.07 mm (0.475 in)
Base diameter12.65 mm (0.498 in)
Rim diameter12.57 mm (0.495 in)
Rim thickness1.07 mm (0.042 in)
Case length27.76 mm (1.093 in)
Overall length35.66 mm (1.404 in)
Ballistic performance
Bullet mass/type Velocity Energy
220 gr (14 g) FMJ 1,200 ft/s (370 m/s) 700 ft⋅lbf (950 J)
Source(s): Textbook of Automatic Pistols [1]

The .45 Mars Long is an experimental centerfire pistol cartridge developed in the late 19th century. The similar .45 Mars Short used the same cupro-nickel-jacketed bullet in a case shortened to 0.66 inch. The bullet has two deep cannelures, and the case is crimped into both. The case mouth is chamfered on the outside to fit flush into the forward cannelure. The cartridge headspaces on this conical forward crimp. This elaborate bullet seating was necessary to withstand the violent feed mechanism of the Mars Automatic Pistol. The case has a thin rim and deep extractor groove in comparison to most rimless pistol cartridges.[1] The Mars cartridges were publicized as the most powerful handgun cartridges through the early 20th century; but fewer than 100 pistols were made and manufacture ceased in 1907.


  1. ^ a b *Wilson, R. K. Textbook of Automatic Pistols, pp.230-231. Plantersville, SC: Small Arms Technical Publishing Company, 1943.
  2. ^ .450 Mars Long Case / MUNICION.ORG

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