.338 Whisper
Encyclopedia
The .338 Whisper is a wildcat cartridge
in the Whisper family, a group of cartridges developed in the early 1990s by J.D. Jones of SSK Industries. Unlike the smaller caliber cartridges in the Whisper family
, loads for the .338 Whisper are mainly limited to subsonic
velocities.
(1128 ft/s at 70°F) to avoid the sonic crack caused by the bullet breaking the sound barrier
which contributes in large part to the overall noise produced when using a firearm. Subsonic loads are often designed to avoid the turbulent transonic
zone entirely. This allows the cartridge to be sound suppressed relatively easily. To ensure terminal performance
at subsonic velocities, heavy bullets for the caliber (250-300 grains) (16.20-19.44g) are desirable. Only those .338 based on the 7mmBR case offer meaningful supersonic velocities.A full house load with fast powder can push a 165 grain Barnes bullet out the barrel at 2520fps. Another favourite pick for such an exercise would be the 180 grain Nosler Accubond or the 200 grain Nosler Ballistic tip traveling out at 2200fps-2350fps. Often found to be too explosive in high power rifles, at such moderate speeds the Ballistic Tips provide both expansion & penetration - this combination with excellent accurancy & a high ballistic coefficient. Of course the silent, subsonic loads should be loaded below the speed of sound with preferably the heaviest & longest bullet the .338 calibre has to offer. Currently this is the Sierra Matchking in 300 grain with a BC of 0.750.
(the most popular cartridge of the family) is often called ".300 Fireball" or ".300-221".
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...
in the Whisper family, a group of cartridges developed in the early 1990s by J.D. Jones of SSK Industries. Unlike the smaller caliber cartridges in the Whisper family
Whisper Family of Firearm Cartridges
The Whisper family of firearm cartridges is a group of wildcat cartridges developed in the early 1990s by J.D. Jones of SSK Industries. The Whisper Family was developed as a line of accurate, multi-purpose cartridges using relatively heavy rifle bullets for a given caliber in subsonic loads...
, loads for the .338 Whisper are mainly limited 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....
velocities.
Versions
There are two versions of the .338 Whisper:- The original .338 Whisper is based on the 7 mm Remington Bench Rest case, necked up (enlarged) to take a .338" bullet. As the 7mm Bench Rest and .308 Winchester.308 WinchesterThe .308 Winchester is a rifle cartridge and is the commercial cartridge upon which the military 7.62x51mm NATO centerfire cartridge is based. The .308 Winchester was introduced in 1952, two years prior to the NATO adoption of the 7.62x51mm NATO T65...
cases share the same case head dimensions, conversion to .338 Whisper from a rifle previously chambered in .308 Winchester (or any cartridge based on the .308 Winchester case, such as .243 Winchester.243 WinchesterThe .243 Winchester is a popular sporting rifle cartridge. Initially designed as a varmint round, it is now more frequently used on medium to large game such as whitetail deer, mule deer, pronghorn, wild hogs, and even black bear and caribou...
, .260 Remington.260 RemingtonThe .260 Remington cartridge was introduced by Remington in 1997. Many wildcat cartridges based on the .308 Winchester case had existed for years before Remington standardized this round...
, 7 mm-08 Remington7 mm-08 RemingtonThe 7mm-08 Remington is a rifle cartridge that is almost a direct copy of a wildcat cartridge developed around 1958 known as the 7mm/308. As these names would suggest, it is the .308 Winchester case necked down to accept 7 mm bullets with a small increase in case length...
, etc...) is a relatively simple task. - The second version (called .338 Whisper #2 by SSK) is based on the .221 Remington Fireball.221 Remington FireballThe .221 Remington Fireball was created by Remington Arms Company in 1963 for use in their single-shot bolt-action pistol called the XP-100. This was a special round designed for an experimental pistol, and has the highest velocity of any commercial pistol cartridge.-History:In the early 1960s...
case, simplifying conversion of firearms chambered in 5.56x45mm or its commercial counterpart, .223 Remington.223 RemingtonThe .223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56×45mm NATO military cartridge. The name is commonly pronounced either two-two-three or two-twenty-three. It is loaded with a diameter, jacketed bullet, with weights ranging from , though the most common...
.
Subsonic
A subsonic cartridge is designed to fire its bullets at velocities slower than the speed of soundSpeed 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....
(1128 ft/s at 70°F) to avoid the sonic crack caused by the bullet breaking the sound barrier
Sound barrier
The sound barrier, in aerodynamics, is the point at which an aircraft moves from transonic to supersonic speed. The term, which occasionally has other meanings, came into use during World War II, when a number of aircraft started to encounter the effects of compressibility, a collection of several...
which contributes in large part to the overall noise produced when using a firearm. Subsonic loads are often designed to avoid the turbulent 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...
zone entirely. This allows the cartridge to be sound suppressed relatively easily. To ensure terminal performance
Terminal ballistics
Terminal ballistics, a sub-field of ballistics, is the study of the behavior of a projectile when it hits its target. It is often referred to as stopping power when dealing with human or other living targets. Terminal ballistics is relevant both for small caliber projectiles as well as for large...
at subsonic velocities, heavy bullets for the caliber (250-300 grains) (16.20-19.44g) are desirable. Only those .338 based on the 7mmBR case offer meaningful supersonic velocities.A full house load with fast powder can push a 165 grain Barnes bullet out the barrel at 2520fps. Another favourite pick for such an exercise would be the 180 grain Nosler Accubond or the 200 grain Nosler Ballistic tip traveling out at 2200fps-2350fps. Often found to be too explosive in high power rifles, at such moderate speeds the Ballistic Tips provide both expansion & penetration - this combination with excellent accurancy & a high ballistic coefficient. Of course the silent, subsonic loads should be loaded below the speed of sound with preferably the heaviest & longest bullet the .338 calibre has to offer. Currently this is the Sierra Matchking in 300 grain with a BC of 0.750.
Trademark
"Whisper" is a registered trademark of SSK Industries. In order to sidestep this branding (and/or any licensing fees required to use the "Whisper" name legally), other manufacturers tend to use different names for cartridges in the Whisper family. For example, .338 Murmer, .338 Phantom and .338 Benchrest. The .300 Whisper.300 Whisper
The .300 Whisper is a wildcat cartridge in the Whisper family, a group of cartridges developed in the early 1990s by J.D. Jones of SSK Industries...
(the most popular cartridge of the family) is often called ".300 Fireball" or ".300-221".
External links
- SSK Industries
- http://sskindustries.com/cartridges.htm
- http://home.xtra.co.nz/hosts/suppress/whisper.htm