.408 Chey Tac
Encyclopedia
The .408 Cheyenne Tactical (or .408 CheyTac) is a specialized rimless
, bottlenecked, centerfire cartridge
for military
long-range sniper rifle
s that was developed by Dr. John D. Taylor and machinist William O. Wordman. It was designed with a possible military need in mind for a cartridge for both the anti-personnel, anti-sniper and anti-materiel role with a (supersonic) precision range of 2,200 yards (2,000 m). It is hoped it will fill in a supposed market niche for long-range cartridges and is offered as a competitor to the most common military NATO long-range service cartridges .338 Lapua Magnum and the .50 BMG
.
, 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 case 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 very pressure resistant cases.
(CIP) or its American equivalent, Sporting Arms and Ammunition Manufacturers' Institute
(SAAMI). Such cartridges are generally known as wildcats
. Wildcat cartridges have no official dimensions nor other performance related specifications. Stated data about wildcats is always informal and using them is at one's own risk.
According to the QuickLOAD
interior ballistics predictor program the cartridge case capacity of the .408 Cheyenne Tactical is about 159 grains (10.32 ml) of water. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action rifles, under extreme conditions. QuickLOAD
states the maximum operating piezo pressure at 63,816 psi
(440 MPa) and shows that this is a wildcat cartridge. The common rifling
twist rate for this cartridge is 330.2 mm (1 in 13 in), eight 0.4080 in grooves, 0.4010 in bore 0.050" land width, square cut, no taper and the primer type
is large rifle.
s.
By blowing out .408 CheyTac factory cases the wildcatter generally hopes to gain extra muzzle velocity by increasing the case capacity of the factory parent cartridge case by a few percent. Practically there can be some muzzle velocity gained by this method, but the measured results between parent cartridges and their 'improved' wildcat offspring is often marginal. An example of a blown out .408 CheyTac variant is the .408 Baer.
Besides changing the shape and internal volume of the parent cartridge case, wildcatters also can change the original caliber. Because the .408 CheyTac offers a large and sturdy, pressure resistant cartridge case it has become quite popular amongst wildcatters. With the .408 CheyTac as the parent case wildcatters have created .338 (.338 Snipe-Tac, 338/408 Baer), .375 (.375 CheyTac, .375-.408 CheyTac, .375 Snipe-Tac, .375 SOE), .416 (.416 PGW) and .510 (.510 Snipe-Tac) caliber variants. The 0.375 inch (9.525 mm) caliber variants currently (2007) seem to attract the most attention. The company that designed the CheyTac Intervention
rifle, CheyTac, LLC, itself offers rifles in a .375 CheyTac chambering in their 2007 retail price list.
nickel
alloy. The factory claims their diameter is accurate to "one 50 millionth" but does not provide a unit of measurement with this claim, making it somewhat vague. One noted downside to the use of solid mono metal projectiles is that they tend to increase the fouling left in the rifle barrel after they are fired. Since the bullets are harder and more abrasive than the gilding metal
jackets of normal jacketed bullets, they are made slightly "undersized" so that they may be gripped effectively by the lands of the barrel's rifling. This inevitably reduces the seal of the bullet in the barrel, allowing hot gunpowder
gases to reach the sides of the projectile, vaporizing some of the material and depositing it in the bore.
Other manufacturers, such as Sierra, Rocky Mountain Bullet Company/Vigilance Rifles, GS Custom Bullets, Lehigh Bullets & Design, Lutz Möller and TTI Armory have developed lead-core or mono metal very-low-drag
projectiles for the .408 CheyTac.
In 2007 Dr. John D. Taylor designed a new class of armor-piercing projectiles (patent pending). The cartridge is called the .408 CheyCorey and in this configuration, it outperforms the .50 AP (both black and silver tips) cartridge against armor steel and titanium. The projectile has a mass of 370 grains (24.0 g). Claimed penetration of AR500 certified steel is 1 inch (2.54 cm) at 100 yards (91.5 m) and 1/2 inch (1.27 cm) at 775 yards (708.8 m).
In 2008 factory loaded .408 CheyTac 420-grain (27.22 g) lead core bullets with 955 copper jackets became available. The very-low-drag bullet
s are made by Rocky Mountain Bullets in Philipsburg, Montana and have a rebated boattail and a claimed ballistic coefficient
(BC) of 0.874.
Factory .408 CheyTac ammunition is expensive, starting at around $7 per round with Jamison International 419-grain (27.15 g) very-low-drag
projectiles.
-measured G1 ballistic coefficient
(BC) for the Lost River Ballistic Technologies/Jamison International 419-grain (27.15 g) bullet of roughly 0.934, though this number has been disputed by a number of knowledgeable sources. Extreme Firearms claimed the G1 BC of the same .408 CheyTac projectile to average 0.945 to 2000 meters and it drops to the low 0.900s to 2800 meters. The .408 CheyTac projectile remains supersonic up to 2,300 yards (2,100 m) according to Extreme Firearms. CheyTac LLC claims that the 26.95 gram (419 gr) projectile has a supersonic range of 2,200+ yards (2,011+ m) at 'standard air conditions'. The average ballistic coefficient of the 419 grain (27.15 g) is 0.945 over 3,825 yards (3,500 m). Jamison International states the G1 BC of this bullet on their website currently (2009) at 0.940.
The above variations can be explained by differences in the ambient air density used for these BC statements or differing range-speed measurements on which the stated G1 BC averages are based. The BC changes during a projectiles flight and stated BC's are always averages for particular range-speed regimes. Some more explanation about the transient nature of a projectile's G1 BC (it rises above or gets under a stated average value for a certain speed-range regime) during flight can be found at the external ballistics
article. This article implies that knowing how a BC was established is almost as important as knowing the stated BC value itself.
region. This is hard to achieve for small arms projectiles. Mathematically you are at a great disadvantage trying to achieve balanced flight with a lead core non mono metal bullet. The rotational mass/surface area ratio is too high."
The balanced flight projectile patent can be found at the US Patent Office, Controlled spin projectile, . According to the patent a projectile engraved and launched according to the teachings of the patented invention should decelerate from supersonic
flight through transonic
to subsonic
in a stable and predictable manner effective to a range beyond 3000 yards (2,743 m). It implies that amongst several other preconditions the rifle barrel has to have specific rifling
dimensions to achieve a desired amount of axial air drag on the bullets surface, which reduces the bullets spinrate to achieve balanced flight. The patent does not account for normally occurring differences in air density. More about balanced flight can also be found in the CheyTac Information Papers.
The Balanced Flight/Controlled Spin Projectile bullet patent has been questioned/disputed by the German physicist Lutz Möller. Mr. Möller realized balanced flight has to do with the nature of spin stabilized flight and scale of parameters. There were projectiles produced prior to the patent that remain stable through the transonic flight regime. This is a consequence of the spin deceleration and forward deceleration of the projectile being similar enough not to cause undesirable precession and yaw during the transonic flight phase. The main parameter for achieving stable transonic transition is controlling the drag coefficient
s (Cd) and forward velocity loss around Mach 1 and to a lesser degree controlling the spin deceleration. In other words, any bullet with appropriate drag behaviour around Mach 1 and mass (distribution) will do exactly what the balanced flight projectile patent states.
) performance from a sniper rifle platform. The Lost River Ballistic Technologies/Jamison International 419-grain (26.95 g) very-low-drag bullet
is the standard, long-range sniping load.
Lost River Ballistic Technologies also designed a 305 grain (19.76 g) bullet for the Battlefield Domination Round (BDR). The BDR is loaded with a 305 grain (19.76 g) bullet (claimed G1 BC = 0.612) and is intended for short and medium range application using the point blank range aiming method.
sea level conditions (air density ρ = 1.225 kg/m³).
For a typical .375 CheyTac chambered gun, shooting 24.30 gram (375 gr) Lost River Ballistic Technologies bullets (claimed G1 BC = 1.02) at 930 m/s (3050 ft/s) muzzle velocity, the supersonic range would be 2230 m (2440 yd) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³).
Improvement beyond this standard while still using standard .375 CheyTac brass is possible, but the bullets have to be very long and the normal cartridge overall length has to be exceeded. The common .375 CheyTac 292 mm (1:11.5 in) rifling twist rate also has to be tightened to stabilize very long projectiles. The use of such a .375 CheyTac based cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and a fast-twist bore. An example of such a special .375 caliber extreme range bullet is the German CNC manufactured mono-metal 26.44 gram (408 gr) .375 Viking (G1 BC 1.537; this Ballistic coefficient (BC) is calculated by its designer, Mr. Lutz Möller, and not proven by Doppler radar
measurements). This bullet has since exhibited dynamic stability problems and is no longer produced. The .375 Viking bullet had an overall length of 70 mm (2.756 in) and derived its anticipated low drag from a radical LD Haack or Sears-Haack
profile in the bullet's nose area. Rifles chambered for this wildcat cartridge, with a cartridge overall length of 119 mm (4.685 in), were to have been equipped with custom made 762 mm (30 in) long 203 mm (1:8 in) twist rate barrels.
In theory, Mr. Möller calculated that a typical .375 CheyTac chambered gun, shooting his now defunct 26.44 gram (408 gr) .375 Viking bullets (claimed G1 BC = 1.537) at 870 m/s (2854 ft/s) muzzle velocity, would have a supersonic range of 3090 m (3380 yd) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³). However, field testing of this projectile proved it to be completely unstable, and useless at any velocity, or range. This was established in February 2009 by Terry Holstine, an Oklahoma State Trooper, who is the only person to ever have fired the Viking. It would appear that Mr. Möller did not test this projectile prior to public release whereby the dynamic instability would have been discovered. The ballistic coefficient of this bullet has never been verified, therefore the supersonic range using this projectile cannot be determined due to the instability and unknown ballistic coefficient regardless of the claims made.
Several high quality large tactical and match (semi) custom bolt actions were designed for the .408 Cheyenne Tactical cartridge and are currently (2007) becoming available. These (semi) custom bolt actions are used with other high grade rifle and sighting components to build custom sporting and target rifles. Such rifles are ordered by long-range accuracy oriented shooters and built by specialized, highly skilled gunsmiths and can cost thousands of dollars. When built to expectation such rifles are very accurate - 0.5 MOA or better consistent accuracy for a particular rifle optimized ammunition is considered normal. Only expert marksmen can make use of this extreme accuracy potential.
Rim (firearms)
A rim is an external flange that is machined, cast, molded, stamped or pressed around the bottom of a firearms cartridge. The rim may serve a number of purposes, the most common being as the place for the extractor to engage...
, bottlenecked, centerfire cartridge
Cartridge (firearms)
A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...
for military
Military
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
long-range sniper rifle
Sniper rifle
In military and law enforcement terminology, a sniper rifle is a precision-rifle used to ensure more accurate placement of bullets at longer ranges than other small arms. A typical sniper rifle is built for optimal levels of accuracy, fitted with a telescopic sight and chambered for a military...
s that was developed by Dr. John D. Taylor and machinist William O. Wordman. It was designed with a possible military need in mind for a cartridge for both the anti-personnel, anti-sniper and anti-materiel role with a (supersonic) precision range of 2,200 yards (2,000 m). It is hoped it will fill in a supposed market niche for long-range cartridges and is offered as a competitor to the most common military NATO long-range service cartridges .338 Lapua Magnum and the .50 BMG
.50 BMG
The .50 Browning Machine Gun or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge...
.
History
The .408 Cheyenne Tactical is based on the .400 Taylor Magnum, which is based on a modified .505 Gibbs505 Gibbs
The 505 Gibbs cartridge was designed by George Gibbs in 1911. The cartridge was originally known as the .505 Rimless Nitro Express or simply as the .505 Rimless. CIP refers to the cartridge as the 505 Mag. Gibbs in their publications...
, 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
Cordite
Cordite is a family of smokeless propellants developed and produced in the United Kingdom from 1889 to replace gunpowder as a military propellant. Like gunpowder, cordite is classified as a low explosive because of its slow burning rates and consequently low brisance...
charges instead of modern smokeless powder
Smokeless powder
Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...
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 case 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
.416 Rigby
The .416 Rigby or 10.6x74mm was designed in 1911 by John Rigby & Company of London, England as a dangerous game cartridge and is the first one to use a bullet with a diameter of .416"...
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 very pressure resistant cases.
Cartridge dimensions
The .408 CheyTac is neither officially registered with nor sanctioned by the Commission Internationale Permanente pour l'Epreuve des Armes à Feu PortativesCommission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives
The Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives is an international organisation whose members are 14 states, mainly European....
(CIP) or its American equivalent, Sporting Arms and Ammunition Manufacturers' Institute
Sporting Arms and Ammunition Manufacturers' Institute
The Sporting Arms and Ammunition Manufacturers' Institute is an association of American firearms and ammunition manufacturers...
(SAAMI). Such cartridges are generally known as wildcats
Wildcat cartridge
A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...
. Wildcat cartridges have no official dimensions nor other performance related specifications. Stated data about wildcats is always informal and using them is at one's own risk.
According to the QuickLOAD
QuickLOAD
QuickLOAD is an internal ballistics predictor computer program for fire arms.For computations apart from other parameters* the cartridge* the used projectile * the gunbarrel length* the cartridge overall length* the used propellant...
interior ballistics predictor program the cartridge case capacity of the .408 Cheyenne Tactical is about 159 grains (10.32 ml) of water. The exterior shape of the case was designed to promote reliable case feeding and extraction in bolt action rifles, under extreme conditions. QuickLOAD
QuickLOAD
QuickLOAD is an internal ballistics predictor computer program for fire arms.For computations apart from other parameters* the cartridge* the used projectile * the gunbarrel length* the cartridge overall length* the used propellant...
states the maximum operating piezo pressure at 63,816 psi
Pounds per square inch
The pound per square inch or, more accurately, pound-force per square inch is a unit of pressure or of stress based on avoirdupois units...
(440 MPa) and shows that this is a wildcat cartridge. The common rifling
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
twist rate for this cartridge is 330.2 mm (1 in 13 in), eight 0.4080 in grooves, 0.4010 in bore 0.050" land width, square cut, no taper and the primer type
Percussion cap
The percussion cap, introduced around 1830, was the crucial invention that enabled muzzleloading firearms to fire reliably in any weather.Before this development, firearms used flintlock ignition systems which produced flint-on-steel sparks to ignite a pan of priming powder and thereby fire the...
is large rifle.
The .408 Cheyenne tactical as parent case
The .408 CheyTac as a wildcat cartridge serves as parent for several other second generation wildcat cartridgeWildcat cartridge
A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...
s.
By blowing out .408 CheyTac factory cases the wildcatter generally hopes to gain extra muzzle velocity by increasing the case capacity of the factory parent cartridge case by a few percent. Practically there can be some muzzle velocity gained by this method, but the measured results between parent cartridges and their 'improved' wildcat offspring is often marginal. An example of a blown out .408 CheyTac variant is the .408 Baer.
Besides changing the shape and internal volume of the parent cartridge case, wildcatters also can change the original caliber. Because the .408 CheyTac offers a large and sturdy, pressure resistant cartridge case it has become quite popular amongst wildcatters. With the .408 CheyTac as the parent case wildcatters have created .338 (.338 Snipe-Tac, 338/408 Baer), .375 (.375 CheyTac, .375-.408 CheyTac, .375 Snipe-Tac, .375 SOE), .416 (.416 PGW) and .510 (.510 Snipe-Tac) caliber variants. The 0.375 inch (9.525 mm) caliber variants currently (2007) seem to attract the most attention. The company that designed the CheyTac Intervention
CheyTac Intervention
The CheyTac Intervention is an American bolt action sniper rifle manufactured by CheyTac LLC for long range soft target interdiction. It is fed by a detachable single stack magazine, which holds 7 rounds. It fires .408 CheyTac or .375 CheyTac ammunition...
rifle, CheyTac, LLC, itself offers rifles in a .375 CheyTac chambering in their 2007 retail price list.
Projectiles (bullets)
Most .408 CheyTac factory ammunition uses solid projectiles or bullets rather than jacketed lead-core bullets, which are common to most other rifle bullets. The oldest factory .408 CheyTac ammunition uses bullets designed by Warren S. Jensen and originally produced by Lost River Ballistic Technologies. Currently (2009) these projectiles are produced by Jamison International, where they are turned on Swiss-type CNC lathes from solid bars of proprietary copperCopper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
alloy. The factory claims their diameter is accurate to "one 50 millionth" but does not provide a unit of measurement with this claim, making it somewhat vague. One noted downside to the use of solid mono metal projectiles is that they tend to increase the fouling left in the rifle barrel after they are fired. Since the bullets are harder and more abrasive than the gilding metal
Gilding metal
Gilding metal is a copper alloy, comprising 95% copper and 5% zinc. Technically, it is a brass.Gilding metal is used for various purposes, including the jackets of bullets, driving bands on some artillery shells, as well as enameled badges and other jewellery....
jackets of normal jacketed bullets, they are made slightly "undersized" so that they may be gripped effectively by the lands of the barrel's rifling. This inevitably reduces the seal of the bullet in the barrel, allowing hot gunpowder
Gunpowder
Gunpowder, also known since in the late 19th century as black powder, was the first chemical explosive and the only one known until the mid 1800s. It is a mixture of sulfur, charcoal, and potassium nitrate - with the sulfur and charcoal acting as fuels, while the saltpeter works as an oxidizer...
gases to reach the sides of the projectile, vaporizing some of the material and depositing it in the bore.
Other manufacturers, such as Sierra, Rocky Mountain Bullet Company/Vigilance Rifles, GS Custom Bullets, Lehigh Bullets & Design, Lutz Möller and TTI Armory have developed lead-core or mono metal very-low-drag
Very-low-drag bullet
Very-low-drag bullets are primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this the projectile must minimize air resistance in flight...
projectiles for the .408 CheyTac.
In 2007 Dr. John D. Taylor designed a new class of armor-piercing projectiles (patent pending). The cartridge is called the .408 CheyCorey and in this configuration, it outperforms the .50 AP (both black and silver tips) cartridge against armor steel and titanium. The projectile has a mass of 370 grains (24.0 g). Claimed penetration of AR500 certified steel is 1 inch (2.54 cm) at 100 yards (91.5 m) and 1/2 inch (1.27 cm) at 775 yards (708.8 m).
In 2008 factory loaded .408 CheyTac 420-grain (27.22 g) lead core bullets with 955 copper jackets became available. The very-low-drag bullet
Very-low-drag bullet
Very-low-drag bullets are primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this the projectile must minimize air resistance in flight...
s are made by Rocky Mountain Bullets in Philipsburg, Montana and have a rebated boattail and a claimed ballistic coefficient
Ballistic coefficient
In ballistics, the ballistic coefficient of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration—a high number indicates a low negative acceleration. BC is a function of mass, diameter, and drag coefficient...
(BC) of 0.874.
Factory .408 CheyTac ammunition is expensive, starting at around $7 per round with Jamison International 419-grain (27.15 g) very-low-drag
Very-low-drag bullet
Very-low-drag bullets are primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this the projectile must minimize air resistance in flight...
projectiles.
Ballistic Coefficient of the Jamison 419 gr projectile
Cheyenne Tactical claimed a Doppler radarDoppler radar
A Doppler radar is a specialized radar that makes use of the Doppler effect to produce velocity data about objects at a distance. It does this by beaming a microwave signal towards a desired target and listening for its reflection, then analyzing how the frequency of the returned signal has been...
-measured G1 ballistic coefficient
Ballistic coefficient
In ballistics, the ballistic coefficient of a body is a measure of its ability to overcome air resistance in flight. It is inversely proportional to the negative acceleration—a high number indicates a low negative acceleration. BC is a function of mass, diameter, and drag coefficient...
(BC) for the Lost River Ballistic Technologies/Jamison International 419-grain (27.15 g) bullet of roughly 0.934, though this number has been disputed by a number of knowledgeable sources. Extreme Firearms claimed the G1 BC of the same .408 CheyTac projectile to average 0.945 to 2000 meters and it drops to the low 0.900s to 2800 meters. The .408 CheyTac projectile remains supersonic up to 2,300 yards (2,100 m) according to Extreme Firearms. CheyTac LLC claims that the 26.95 gram (419 gr) projectile has a supersonic range of 2,200+ yards (2,011+ m) at 'standard air conditions'. The average ballistic coefficient of the 419 grain (27.15 g) is 0.945 over 3,825 yards (3,500 m). Jamison International states the G1 BC of this bullet on their website currently (2009) at 0.940.
The above variations can be explained by differences in the ambient air density used for these BC statements or differing range-speed measurements on which the stated G1 BC averages are based. The BC changes during a projectiles flight and stated BC's are always averages for particular range-speed regimes. Some more explanation about the transient nature of a projectile's G1 BC (it rises above or gets under a stated average value for a certain speed-range regime) during flight can be found at the external ballistics
External ballistics
External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. External ballistics is frequently associated with firearms, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target.-Forces...
article. This article implies that knowing how a BC was established is almost as important as knowing the stated BC value itself.
Balanced-flight / controlled-spin projectile
Lost River Ballistic Technologies (statement of Mr. Warren Jensen) stated that "the .408 CheyTac is the first bullet/rifle system that utilizes what they call a balanced flight projectile. To achieve balanced flight the linear drag has to be balanced with the rotational drag to keep the very fine nose (meplat) of the bullet pointed directly into the oncoming air. It should result in very little precession and yaw at extreme range and allows accurate flight back through the transonicTransonic
Transonic speed is an aeronautics term referring to the condition of flight in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil that are concurrently below, at, and above the speed of sound in the range of Mach 0.8 to 1.2, i.e. 600–900 mph...
region. This is hard to achieve for small arms projectiles. Mathematically you are at a great disadvantage trying to achieve balanced flight with a lead core non mono metal bullet. The rotational mass/surface area ratio is too high."
The balanced flight projectile patent can be found at the US Patent Office, Controlled spin projectile, . According to the patent a projectile engraved and launched according to the teachings of the patented invention should decelerate from supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...
flight through transonic
Transonic
Transonic speed is an aeronautics term referring to the condition of flight in which a range of velocities of airflow exist surrounding and flowing past an air vehicle or an airfoil that are concurrently below, at, and above the speed of sound in the range of Mach 0.8 to 1.2, i.e. 600–900 mph...
to subsonic
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....
in a stable and predictable manner effective to a range beyond 3000 yards (2,743 m). It implies that amongst several other preconditions the rifle barrel has to have specific rifling
Rifling
Rifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
dimensions to achieve a desired amount of axial air drag on the bullets surface, which reduces the bullets spinrate to achieve balanced flight. The patent does not account for normally occurring differences in air density. More about balanced flight can also be found in the CheyTac Information Papers.
The Balanced Flight/Controlled Spin Projectile bullet patent has been questioned/disputed by the German physicist Lutz Möller. Mr. Möller realized balanced flight has to do with the nature of spin stabilized flight and scale of parameters. There were projectiles produced prior to the patent that remain stable through the transonic flight regime. This is a consequence of the spin deceleration and forward deceleration of the projectile being similar enough not to cause undesirable precession and yaw during the transonic flight phase. The main parameter for achieving stable transonic transition is controlling the drag coefficient
Drag coefficient
In fluid dynamics, the drag coefficient is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment such as air or water. It is used in the drag equation, where a lower drag coefficient indicates the object will have less aerodynamic or...
s (Cd) and forward velocity loss around Mach 1 and to a lesser degree controlling the spin deceleration. In other words, any bullet with appropriate drag behaviour around Mach 1 and mass (distribution) will do exactly what the balanced flight projectile patent states.
Performance
The cartridge delivers accurate (sub-MOAMinute of arc
A minute of arc, arcminute, or minute of angle , is a unit of angular measurement equal to one sixtieth of one degree. In turn, a second of arc or arcsecond is one sixtieth of one minute of arc....
) performance from a sniper rifle platform. The Lost River Ballistic Technologies/Jamison International 419-grain (26.95 g) very-low-drag bullet
Very-low-drag bullet
Very-low-drag bullets are primarily a small arms ballistics development of the 1980s–1990s, driven by shooters' desire for bullets that will give a higher degree of accuracy and kinetic efficiency, especially at extended ranges. To achieve this the projectile must minimize air resistance in flight...
is the standard, long-range sniping load.
Lost River Ballistic Technologies also designed a 305 grain (19.76 g) bullet for the Battlefield Domination Round (BDR). The BDR is loaded with a 305 grain (19.76 g) bullet (claimed G1 BC = 0.612) and is intended for short and medium range application using the point blank range aiming method.
Supersonic range
For a typical .408 CheyTac chambered gun, shooting 27.15 gram (419 gr) Lost River Ballistic Technologies bullets (claimed G1 BC = 0.940) at 884 m/s (2900 ft/s) muzzle velocity, the supersonic range would be 1930 m (2110 yd) under International Standard AtmosphereInternational Standard Atmosphere
The International Standard Atmosphere is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes. It has been established to provide a common reference for temperature and pressure and consists of tables of...
sea level conditions (air density ρ = 1.225 kg/m³).
For a typical .375 CheyTac chambered gun, shooting 24.30 gram (375 gr) Lost River Ballistic Technologies bullets (claimed G1 BC = 1.02) at 930 m/s (3050 ft/s) muzzle velocity, the supersonic range would be 2230 m (2440 yd) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³).
Improvement beyond this standard while still using standard .375 CheyTac brass is possible, but the bullets have to be very long and the normal cartridge overall length has to be exceeded. The common .375 CheyTac 292 mm (1:11.5 in) rifling twist rate also has to be tightened to stabilize very long projectiles. The use of such a .375 CheyTac based cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and a fast-twist bore. An example of such a special .375 caliber extreme range bullet is the German CNC manufactured mono-metal 26.44 gram (408 gr) .375 Viking (G1 BC 1.537; this Ballistic coefficient (BC) is calculated by its designer, Mr. Lutz Möller, and not proven by Doppler radar
Doppler radar
A Doppler radar is a specialized radar that makes use of the Doppler effect to produce velocity data about objects at a distance. It does this by beaming a microwave signal towards a desired target and listening for its reflection, then analyzing how the frequency of the returned signal has been...
measurements). This bullet has since exhibited dynamic stability problems and is no longer produced. The .375 Viking bullet had an overall length of 70 mm (2.756 in) and derived its anticipated low drag from a radical LD Haack or Sears-Haack
Sears-Haack body
The Sears–Haack body is the aerodynamic body shape with the lowest theoretical wave drag. Aircraft designed to operate at high subsonic or supersonic speeds have their cross-sectional areas designed to match as closely as possible the proportions of Sears-Haack body.By Whitcomb's area rule, the...
profile in the bullet's nose area. Rifles chambered for this wildcat cartridge, with a cartridge overall length of 119 mm (4.685 in), were to have been equipped with custom made 762 mm (30 in) long 203 mm (1:8 in) twist rate barrels.
In theory, Mr. Möller calculated that a typical .375 CheyTac chambered gun, shooting his now defunct 26.44 gram (408 gr) .375 Viking bullets (claimed G1 BC = 1.537) at 870 m/s (2854 ft/s) muzzle velocity, would have a supersonic range of 3090 m (3380 yd) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m³). However, field testing of this projectile proved it to be completely unstable, and useless at any velocity, or range. This was established in February 2009 by Terry Holstine, an Oklahoma State Trooper, who is the only person to ever have fired the Viking. It would appear that Mr. Möller did not test this projectile prior to public release whereby the dynamic instability would have been discovered. The ballistic coefficient of this bullet has never been verified, therefore the supersonic range using this projectile cannot be determined due to the instability and unknown ballistic coefficient regardless of the claims made.
| Cartridge | Bullet weight gr | Muzzle velocity Muzzle velocity Muzzle velocity is the speed a projectile has at the moment it leaves the muzzle of the gun. Muzzle velocities range from approximately to in black powder muskets , to more than in modern rifles with high-performance cartridges such as the .220 Swift and .204 Ruger, all the way to for tank guns... ft/s (m/s) | Muzzle energy Muzzle energy Muzzle energy is the kinetic energy of a bullet as it is expelled from the muzzle of a firearm. It is often used as a rough indication of the destructive potential of a given firearm or load... ft·lbf (J) |
|---|---|---|---|
| .338 Lapua Magnum | 250 | 2970 (905) | 4,893 (6,634) |
| .338 Lapua Magnum | 300 | 2717 (828) | 4,919 (6,669) |
| .408 CheyTac | 305 | 3500 (1067) | 8,298 (11,251) |
| .408 CheyTac | 419 | 3000 (915) | 8,376 (11,356) |
| .416 Barrett .416 Barrett The .416 Barrett or 10.6x83mm centerfire rifle cartridge is a proprietary bottlenecked centrefire rifle cartridge designed in 2005. It is an alternative to the .50 BMG in long-range high-caliber rifles. It was designed in response to a request for a medium/heavy rifle/cartridge combination that was... |
400 | 3250 (990) | 9,380 (12,718) |
| .50 BMG .50 BMG The .50 Browning Machine Gun or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge... |
700 | 2978 (907) | 13,971 (18,942) |
Chambering availability
The .408 Cheyenne Tactical chambering is offered for these factory rifles:- BCM Europearms S.a.s.
- CheyTac Intervention rifle seriesCheyTac InterventionThe CheyTac Intervention is an American bolt action sniper rifle manufactured by CheyTac LLC for long range soft target interdiction. It is fed by a detachable single stack magazine, which holds 7 rounds. It fires .408 CheyTac or .375 CheyTac ammunition...
- CheyTac LLC. - E.D.M. Arms XM04
- PGWDTI Timberwolf .408 CheyTac and .416 PGW rifle - Prairie Gun Works Defence Technologies Inc.Prairie Gun WorksPrairie Gun Works Defence Technologies Inc., also known as PGWDTI, is a small company in Winnipeg, Manitoba, Canada that specializes in building state of the art military grade sniper weapon systems, sound suppressors and associated components....
- Lawton Machine LLC. (Lawton Rifle Barrels)
- Lobaev Sniper RifleLobaev Sniper RifleThe Lobaev sniper rifle is a rifle line of custom built bolt action sniper rifles manufactured at a small, private company named "Tsar-Cannon Ltd" , which produces benchrest equipment and long-range, sniper and mountain hunting rifles in Tarusa, Russia. Machinery used to produce these rifles was...
- Grande Armeria Camuna precision rifles
- RND Manufacturing, Inc.
- Tactilite T1 (single-shot) AR-15AR-15The AR-15 is a lightweight, 5.56 mm, air-cooled, gas-operated, magazine-fed semi-automatic rifle, with a rotating-lock bolt, actuated by direct impingement gas operation. It is manufactured with the extensive use of aluminum alloys and synthetic materials....
.408 Chey Tac upper - THOR XM408THOR XM408The THOR XM408 is an American-made bolt action heavy sniper rifle designed by THOR Global Defense Group and EDM Arms for long range soft target and hard target interdiction ....
- Vigilance Rifles VR1
Several high quality large tactical and match (semi) custom bolt actions were designed for the .408 Cheyenne Tactical cartridge and are currently (2007) becoming available. These (semi) custom bolt actions are used with other high grade rifle and sighting components to build custom sporting and target rifles. Such rifles are ordered by long-range accuracy oriented shooters and built by specialized, highly skilled gunsmiths and can cost thousands of dollars. When built to expectation such rifles are very accurate - 0.5 MOA or better consistent accuracy for a particular rifle optimized ammunition is considered normal. Only expert marksmen can make use of this extreme accuracy potential.
See also
- CheyTac InterventionCheyTac InterventionThe CheyTac Intervention is an American bolt action sniper rifle manufactured by CheyTac LLC for long range soft target interdiction. It is fed by a detachable single stack magazine, which holds 7 rounds. It fires .408 CheyTac or .375 CheyTac ammunition...
- 10 mm caliber10 mm caliberThis article lists firearm cartridges which have a bullet in the caliber range.*Length refers to the cartridge case length.*OAL refers to the overall length of the cartridge.All measurements are in mm .-Pistol cartridges:...
- .338 Lapua Magnum
- .416 Barrett.416 BarrettThe .416 Barrett or 10.6x83mm centerfire rifle cartridge is a proprietary bottlenecked centrefire rifle cartridge designed in 2005. It is an alternative to the .50 BMG in long-range high-caliber rifles. It was designed in response to a request for a medium/heavy rifle/cartridge combination that was...
- List of sniper rifles
- List of individual weapons of the U.S. Armed Forces