.408 Cheyenne Tactical

.408 Cheyenne Tactical
.408 Cheyenne Tactical cartridge
Type	Rifle
Place of origin	United States
Production history
Designer	John Taylor and William O. Wordman
Designed	2001
Manufacturer	CheyTac USA LLC[1]
Produced	2001–present
Variants	.375 CheyTac
Specifications
Parent case	.505 Gibbs/.400 Taylor Magnum
Case type	Rimless, bottleneck
Bullet diameter	10.36 mm (0.408 in)
Land diameter	10.16 mm (0.400 in)
Neck diameter	11.12 mm (0.438 in)
Shoulder diameter	15.24 mm (0.600 in)
Base diameter	16.18 mm (0.637 in)
Rim diameter	16.25 mm (0.640 in)
Rim thickness	1.60 mm (0.063 in)
Case length	77.21 mm (3.040 in)
Overall length	115.50 mm (4.547 in)
Case capacity	10.32 cm3 (159.3 gr H2O)
Rifling twist	330.2 mm (1 in 13 in)
Primer type	Large rifle
Maximum pressure (C.I.P. (2013–2021))	440.00 MPa (63,817 psi)
Ballistic performance
Bullet mass/type Velocity Energy 305 gr (20 g) Solid 3,500 ft/s (1,100 m/s) 8,295 ft⋅lbf (11,247 J) 419 gr (27 g) Solid 3,000 ft/s (910 m/s) 8,373 ft⋅lbf (11,352 J)
Source(s): Cartridges of the World[2]

The .408 Cheyenne Tactical (designated 408 Chey Tac (10.36×77mm) by the C.I.P.)^[3] is a specialized rimless, bottlenecked, centerfire cartridge for military long-range sniper rifles that was developed by Dr. John D. Taylor and machinist William O. Wordman. The round was designed with a possible military need for a cartridge for anti-personnel, anti-sniper, and anti-materiel roles with a (supersonic) precision range of 2,200 yards (2,000 m). It is offered as a competitor to the most common military NATO long-range service cartridges, such as .338 Lapua Magnum and the .50 BMG.