The .338 Whisper is a

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

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.User "Review" on the .338 ammo
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Versions

There are three versions of the .338 Whisper: #The original .338 Whisper #1 (metric: 8.6x38mm) is based on the

7mm BR Remington The 7mm BR Remington, commonly called the 7mm BR or the 7mm Benchrest Remington in long form, was a cartridge developed by Remington for the Remington XP-100 single-shot bolt-action handgun. The cartridge was developed for the Unlimited Class in ...

case, necked up (enlarged) to take a .338" bullet. As the 7mm Bench Rest and

.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 ...

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, .260 Remington, 7 mm-08 Remington, etc...) is a relatively simple task.http://www.reloadersnest.com/frontpage.asp?CaliberID=389 Information on the two different whisper versions #The second version (called .338 Whisper #2 by SSK, metric: 8.6x35mm) is based on the .221 Remington Fireball case, simplifying conversion of firearms chambered in 5.56×45mm or its commercial counterpart,

.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 ...

Subsonic

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 wel ...

(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 ...

, 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 (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 transonic ...

zone (~900ft/s - 1350ft/s or 0.8 to 1.2

mach Mach may refer to Mach number, the speed of sound in local conditions. It may also refer to: Computing * Mach (kernel), an operating systems kernel technology * ATI Mach, a 2D GPU chip by ATI * GNU Mach, the microkernel upon which GNU Hurd is bas ...

) entirely. This allows the firearm to be suppressed relatively easily. To ensure terminal performance at subsonic velocities, heavy bullets for the caliber () are desirable. Of course the silent, subsonic loads should be loaded below the speed of sound with preferably the heaviest and longest bullet the .338 calibre has to offer. Currently this is the Berger Hybrid Open Tip Match (OTM) with a BC of 0.818 and a length of .

Supersonic

Only those .338 based on the 7mmBR case offer meaningful supersonic velocities. A full power load with fast powder can push a Barnes bullet to a muzzle velocity of . Another favourite pick for such an exercise would be the Nosler Accubond or the Nosler Ballistic tip traveling at . Often found to be too explosive in high power rifles, at such moderate speeds the Ballistic Tips provide both expansion and penetration - this combination with excellent accuracy and a high ballistic coefficient.

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 Murmur, .338 Phantom and .338 Benchrest. The

.300 Whisper The .300 Whisper is a CIP standard cartridge in the Whisper family, a group of cartridges developed in the early 1990s by J.D. Jones of SSK Industries. It was developed as a multi-purpose cartridge, capable of utilizing relatively lightweight ...

(the most popular cartridge of the family) is often called ".300 Fireball" or ".300-221".

References

External links