The .338 Whisper (8.59x38mm) is a

wildcat cartridge A wildcat cartridge, often shortened to wildcat, is a custom-made cartridge (weaponry), cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created as experimental variants to optimize a certain ballis ...

in the Whisper family, a group of cartridges developed in the early 1990s by

J.D. Jones J. D. Jones (born November 21, 1936) is an American firearms and cartridge designer, firearms writer and founder of SSK Industries. Jones began hunting at an early age, and became interested in bullet casting and handloading firearms cartrid ...

SSK Industries SSK Industries, Inc. is an American designer and manufacturer of firearms and accessories in Wintersville, Ohio. Founded in 1977, the company is known for its custom Contender and Encore barrels. Started by hunter and gun enthusiast J. D. Jones ...

. Unlike the smaller caliber cartridges in the Whisper family, loads for the .338 Whisper are mainly limited to

subsonic Subsonic may refer to: Motion through a medium * Any speed lower than the speed of sound within a sound-propagating medium * Subsonic aircraft, a flying machine that flies at air speeds lower than the speed of sound * Subsonic ammunition, a type o ...

velocities.User "Review" on the .338 ammo
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Versions

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

7mm BR Remington The 7mm BR Remington / 7.2x38mm, commonly called the 7mm BR or the 7mm Benchrest Remington in long form, was an intermediate cartridge developed by Remington for the Remington XP-100 single-shot bolt-action handgun. The cartridge was developed ...

case, necked up (enlarged) to take a .338" bullet. As the 7mm Bench Rest and .308 Winchester 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 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...) 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.

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 elasticity (solid mechanics), elastic medium. More simply, the speed of sound is how fast vibrations travel. At , the speed of sound in a ...

(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 speed, supersonic airflow around that object. The exact range of speeds depends on the object's critical Mach numb ...

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

mach The Mach number (M or Ma), often only Mach, (; ) is a dimensionless quantity in fluid dynamics representing the ratio of flow velocity past a Boundary (thermodynamic), boundary to the local speed of sound. It is named after the Austrian physi ...

) 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

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

References

External links