The Whisper family of firearm cartridges is a group of

wildcat cartridge A wildcat cartridge, often shortened to wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic (such as the power, s ...

s 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 A rifle is a long-barreled firearm designed for accurate shooting, with a barrel that has a helical pattern of grooves ( rifling) cut into the bore wall. In keeping with their focus on accuracy, rifles are typically designed to be held with ...

bullets for a given caliber in subsonic loads. The intention was to create an extremely accurate cartridge family for military, police, competition and specialized hunting markets that could also be easily sound suppressed. While all cartridges in the Whisper family must be capable of accuracy using subsonic loads, most of the smaller caliber cartridges of the family (.308" and under) are also capable of being loaded to supersonic velocities using relatively lightweight bullets for their caliber, increasing their utility.

Subsonic cartridges

A subsonic cartridge is designed to fire its bullets at velocities slower than the

speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends strongly on temperature as w ...

(1128 ft/s at 70 °F) to avoid the sonic crack caused by the bullet breaking the

sound barrier The sound barrier or sonic barrier is the large increase in aerodynamic drag and other undesirable effects experienced by an aircraft or other object when it approaches the speed of sound. When aircraft first approached the speed of sound, th ...

. This allows the cartridge to be sound suppressed relatively easily. Additionally, in some cases, subsonic loads are often intended to avoid the turbulent

transonic Transonic (or transsonic) flow is air flowing around an object at a speed that generates regions of both subsonic and supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach number, but transoni ...

zone entirely, maximizing potential accuracy.

Thumper concept

The Whisper rounds exceeding a caliber of .45 in (11.6mm) are in accordance with the Thumper concept popularized by Jeff Cooper.

Whisper cartridge cases

Yet another consideration of the Whisper Family design is that all of the cartridges are based on existing cases that utilize common case head dimensions. This allows rifles with common bolt face dimensions to be converted to a Whisper cartridge fairly easily, often requiring only the rifle's action to be re-barreled. There are four "series" within the Whisper Family, each using a different parent case. *The .221 Fireball case shares the same case head dimensions (0.375"/ 9.53mm) as the commercial

.223 Remington The .223 Remington (designated as the 223 Remington by the SAAMI and 223 Rem by the CIP) is a rimless, bottlenecked rifle cartridge. It was developed in 1957 by Remington Arms and Fairchild Industries for the U.S. Continental Army Command ...

and military 5.56×45mm cartridges. *The 7mm Remington Bench Rest case shares the same case head dimensions (0.470"/ 11.94mm) as the commercial

.308 Winchester The .308 Winchester is a smokeless powder rimless bottlenecked rifle cartridge widely used for hunting, target shooting, police, military, and personal protection applications globally. It is similar but not identical to the 7.62×51mm NATO ...

(as well as other cartridges based on that case; .243 Winchester,

.260 Remington The .260 Remington (also known as 6.5-08 A-Square) 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. Because 6.5 mm ( ...

7mm-08 Remington The 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 (.284) bullets wit ...

, etc.) and military 7.62×51 NATO cartridges. *The .338 Lapua Magnum case also has a fairly unusual case head diameter (0.590"/ 14.99mm). However, the vast majority of rifles chambered for the .338 Lapua Magnum are bolt actions and as such can be chambered in .510 Whisper via a relatively simple re-barrelling. As the manufacture of .338 Lapua Magnum ammunition would appear to be going nowhere but up (due to several militaries adopting it for their sniper rifles), this may be a reason behind the development of a Whisper cartridge based on its case—more available and more economical brass. The .338 Lapua Magnum case by itself has been based on the

.416 Rigby The .416 Rigby is a rifle cartridge designed in 1911 by London based gunmaker John Rigby & Company, for hunting dangerous game. It is the first cartridge to use a bullet of .416 inch (10.57 mm) diameter. The rifles, as built by John Rigby & Co ...

. *The .460 Weatherby Magnum has a case head diameter (0.580"/ 14,73mm) unique to the large Weatherby belted magnum cases. Few other cartridges use this case head size (or something close, like the .416 Rigby). This tends to mean that rifles capable of being converted are somewhat less available or are based on expensive custom actions. Also, cases for forming tend to be ''very'' expensive. The .460 Weatherby Magnum case by itself has been based on the .378 Weatherby Magnum.

Mini and Micro Whispers

There are also two little-known cartridges of the Whisper Family based on handgun cartridge cases. These are the 7.62 Micro Whisper, based on the .30 Luger case; and the 7.63 Mini-Whisper, based on the .30 Mauser case. Like the rest of the Whisper Family, these two cartridges are designed to fire rifle bullets at subsonic velocities.

Trademark

SSK Industries has a registration for the

wordmark __notoc__ A wordmark, word mark, or logotype, is usually a distinct text-only typographic treatment of the name of a company, institution, or product name used for purposes of identification and branding. Examples can be found in the graphic iden ...

"Whisper" (reg. no. 1898840) in class 13 (ammunition). In order to sidestep this branding and/or avoid licensing fees required to use the "Whisper" name legally, other manufacturers tend to use different names for cartridges in the Whisper family. For example, the .300 Whisper, the most popular cartridge of the family, is often called

.300 AAC Blackout The .300 AAC Blackout (designated as the 300 BLK by the SAAMI and 300 AAC Blackout by the C.I.P. or 300 AAC Blackout'' C.I.P. TDCC sheet 300 ACC Blackout/ref>), also known as 7.62×35mm, is an intermediate cartridge developed in the United Sta ...

, ".300 AAC", ".300 Fireball", ".300 warrior carbine", or ".300-221".

References

{{Reflist

External links

SSK Industries
Cartridge families Wildcat cartridges