8.5mm Mars

The 8.5mm Mars is an experimental centerfire pistol cartridge developed in the late 19th century based on necking down the .45 Mars Long case. 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. This elaborate bullet seating was necessary to withstand the violent feed mechanism of the Mars Automatic Pistol. The cartridge headspaces on the shoulder adjacent to the neck. The case has a thin rim and deep extractor groove in comparison to most rimless pistol cartridges. There was a very similar 9mm Mars cartridge firing a 156 gr (10.1 g; 0.36 oz) bullet at 1,400 ft/s (430 m/s). 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.

8.5mm Mars
Type	Pistol
Place of origin	United Kingdom
Production history
Designed	1899
Manufacturer	Kynoch
Specifications
Case type	Rimless, bottleneck
Bullet diameter	8.41 mm (0.331 in)
Neck diameter	9.10 mm (0.358 in)
Shoulder diameter	10.60 mm (0.417 in)
Base diameter	10.70 mm (0.421 in)
Rim diameter	10.40 mm (0.409 in)
Rim thickness	0.90 mm (0.035 in)
Case length	26.00 mm (1.024 in)
Overall length	36.80 mm (1.449 in)
Ballistic performance
Bullet mass/type Velocity Energy 139 gr (9 g) FMJ 1,550 ft/s (470 m/s) 740 ft⋅lbf (1,000 J)
Source(s): Textbook of Automatic Pistols MUNICION.ORG

See also

• 8mm caliber