The 408 cheytac Tac (10.4×77mm) as it is commonly known, or by its full name, .408 Cheyenne Tactical, is a counter-sniper rifle cartridge, developed by Dr SBR ammunition is match-grade quality 408 cheytac and is used by top level shooters like Team Smith & Wesson’s BJ Norris. Here’s what BJ had to say about SBR Ammunition:
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“Having fired well over 300,000 rounds during my career as a competitive pistol shooter, I have specific things I look for in ammunition. It must be accurate, consistent, and above all totally reliable. SBR Ammunition fits these descriptions perfectly. Developed and manufactured on state of the art equipment, each load goes through an exhaustive testing process before being packaged and marketed. Quality ammunition is a passion of Buddy Singleton and it shows up in every aspect of SBR’s products, from the LaserMatch Tracers to the Special-Application-Subsonic rounds designed specifically for suppressors, you can trust SBR to deliver their best in every box, I know I do.”
The .408 Cheyenne Tactical (designated 408 Chey Tac (10.36×77mm) by the C.I.P. from 2013 to 2021) 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.
This ammunition is new production, non-corrosive, in boxer primed, reloadable brass cases.
The .408 Cheyenne Tactical is based on the .400 Taylor Magnum, which itself is based on a modified .505 Gibbs, necked down to 0.408 inches (10.36 mm). The .505 Gibbs is an old English big game cartridge that was designed to accommodate 39,160 psi (270 MPa) pressure. One of the disadvantages to these old cartridge cases intended for firing cordite charges instead of modern smokeless powder is the thickness of the sidewall just forward to the web.
During ignition, the cartridge’s base, forward to the bolt face, is not supported. The case is driven back against the bolt face which results in the stretching of the case, particularly the sidewall immediately forward of the web. When the sidewall resists the outward expansion against the chamber, the pressure stretches the case thereby increasing its length resulting in the sidewall becoming thinner at that stretch point.
In the .408 CheyTac cartridge casing design particular attention was directed toward thickening and metallurgically strengthening the case’s web and sidewall immediately forward to the web to accommodate high chamber pressures. In modern solidhead cases, the hardness of the brass is the major factor that determines a case’s pressure limit before undergoing plastic deformation. Lapua Ltd. solved this problem when they used the .416 Rigby as the parental case to the .338 Lapua Magnum.
They created a hardness distribution ranging from the head and web (hard) to the mouth (soft) as well as a strengthened (thicker) case web and sidewall immediately forward of the web. This method results in a very pressure resistant case.
The .408 Cheyenne Tactical became officially registered by the Commission Internationale Permanente pour l’Epreuve des Armes à Feu Portatives (C.I.P.) on 15 May 2013 ending its status as a wildcat cartridge. In 2020 it was deregistered by the C.I.P.
The 416 cheytac has 10.32 ml (159 grains H2O) cartridge case capacity.
.408 Cheyenne Tactical maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).
Americans would define the shoulder angle at alpha/2 ≈ 22.13 degrees. The common rifling twist rate for this cartridge is 330.2 mm (1 in 13 in), 8 grooves, Ø lands = 10.16 mm (0.400 in), Ø grooves = 10.36 mm (0.408 in), land width = 2.57 mm (0.1 in) and the primer type is large rifle.
how loud is a 408 cheytac
According to the official C.I.P. (Commission Internationale Permanente pour l’Epreuve des Armes à Feu Portatives) rulings the .408 Cheyenne Tactical can handle up to 440.00 MPa (63,817 psi) Pmax piezo pressure. In C.I.P. regulated countries every rifle cartridge combo has to be proofed at 125% of this maximum C.I.P. pressure to certify for sale to consumers. This means that .408 Cheyenne Tactical chambered arms in C.I.P. regulated countries are currently (2016) proof tested at 550.00 MPa (79,771 psi) PE piezo pressure.