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Note: The material on this page was provided by J.D. Jones
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After considerable frustration on my part, I have finally managed to get a new forum up and running. The forum includes two areas, one for area for 300 Whisper rifles and pistols and a second for reloading and ammo issues. I have a huge number of visitors that come to these pages each day so please drop in the forum and say "Hi" and share your projects!

Click HERE to go to SSK Industries

Click HERE to go to SSK Industries

The 300 Whisper® is a new concept in the development of small case capacity, highly efficient cartridges combined with bullets of extreme ballistic efficiency.

The 300 Whisper® was designed for the purpose of firing extremely heavy, accurate, ballistically efficient bullets at sub-sonic velocities and is now the state of the art long range cartridge in suppressed weapons. It delivers more energy more accurately than any existing sub-sonic round at 200 yards {and a lot further} (except other Whispers®). In addition, it has interesting sonic capabilities - possessing greater versatility than any other cartridge capable of performing in these vastly differing arenas.

Powder charges are very small allowing the use of small suppressors. The 240 grain Sierra Matchking launched at a muzzle velocity of 1040 FPS/576 foot pounds energy arrives at 200 yards with a velocity of 976 FPS/508 FPE while maintaining minute of angle accuracy from bolt action rifles and many autos. Suppressed, most of the "noise" heard by the firer is that of the firing pin striking and action "tightening up" under the stress generated. With suppressors there is some small amount of muzzle noise. In this mode there is no audible sound made by the bullet as it is under the speed of sound and does not generate a sonic boom. Unsuppressed, with heavy bullets, the sound of firing is less than that of a 9MM pistol.

Sub-sonic as well as sonic accuracy is maintained with bullets weighing 125, 150, 168, 180, 190, 200, 220 and 240 grains from the same barrel. 200, 220 and 240-grain sub-sonic bullets usually tumble shortly after impact creating wounds far in excess of their "paper" ballistics. Special purpose projectile ammunition is also available on special request. A "helmet puncher" is now under development.

"Upper" receivers for the AR-15/M-16 made by SSK utilize 100% AR-15/ M-16 parts with the exception of the 30-caliber barrel and gas system. The gas system may be a fixed system which operates the weapon normally or an adjustable four position system which incorporates a cut off for very silent operation in the suppressed sub-sonic mode, a port which develops a rate of fire in full auto of about 750 RPM, another for operation under dirty conditions to assure reliability and another special purpose port. Pulling the pins and replacing the original "upper" unit with the SSK Whisper® unit converts the AR-15/M-16 to 30 caliber. Standard M-16 magazines are used. Accuracy, power and control of the weapon in full auto sub-sonic mode is simply unmatched by any other weapon of this type. In sub-sonic sub-machine gun mode, it far exceeds any other similar purpose sub-machine gun cartridge and weapon system.

 Subsonic Loads Velocity/Energy
















































Supersonic Loads Velocity/Energy































In addition to its sub-sonic role, the 300 Whisper® has the ability to perform several sonic velocity roles. Ammunition utilizing 125 grain Ballistic Tip Bullets at 2400 FPS/1598 FPE and all other weights through 240 grain bullets at 1375 FPS/1005 FPE operates through all of the guns without the need for modification. Supersonic ammunition will create a ballistic "crack" even with a suppressed weapon. However the '"crack" of the bullet is non directional - you can't tell the origin of the shot.

Shorty, Standard and Match Grade AR-15/M-16 units are available. Stainless match grade barrels are our "standard" for suppressed use. SSK suppressers are also of stainless construction.

The Thompson Center Contender in both pistol and carbine versions are naturals for this caliber and are inexpensive. Most guns originally chambered for the 223 (5.56 MM) round can be converted to the 300 Whisper®. The lnterarms Mini-Mark X and Sako actions make up into particularly nice small rifles suitable for both the counter sniper role and for hunting.

In super-sonic mode, the 300 Whisper® essentially ballistically duplicates the 7.62. x 39 Russian round with far better and more accurate bullets than usually found in the Russians .310-.311 bullet diameter. It makes an excellent 200-250 yard deer cartridge in very lightweight rifles with very little recoil making it an excellent choice for any individual who may be sensitive to recoil. As a recreational cartridge it is accurate, has a low noise level in any mode, and with the heavier bullets is capable of 100% performance on Silhouette Ram targets. The 300 Whisper® utilizes the 221 Fireball case opened to 30 caliber as its parent cartridge.

SSK is currently accepting orders for bolt action rifles in several varieties, AR-15/M-16 complete guns or upper units, Contender barrels or complete guns. Reloading dies are in stock. Sound suppressors in a variety of configurations are available.

J. D. Jones is the inventor of the 300 Whisper®. There are other Whisper® cartridges at every caliber step from 22 through 50. Data on them will be released as is found appropriate. Serious inquiries regarding the 500 Whisper® (sub-sonic 750/1040 FPS or sonic 750/ 2000 FPS) from a lightweight repeating rifle will be answered on an individual basis.

COR-BON is producing loaded ammunition in a variety of weights and velocities ranging from 125/2400 through the 240/1040 velocity range. Ammunition is available from SSK.

SIGHTS: Any iron, optical or electronic sight seems to work well. Personally, I prefer modified Leupold scopes with multiple dots for each 50-yard increment from 50 through 300 yards for subsonic usage.

Handloading the 300 Whisper®:

Unfired 221 Fireball cases are first neck expanded to 30 caliber; then full length resized in the 300 Whisper® die which corrects any neck misalignment due to neck expanding. Case mouths should be chamfered although this is considered a superfluous optional procedure by some. Normal priming with small rifle primers, (I prefer the Remington 7-1/2) charging with powder and normal seating of the bullet completes the procedure.

There are no surprises in loading the 300 Whisper®. However, you should note normal lot to lot variations in components can and do make substantial differences when loading sub-sonic ammunition. The speed of sound here at the shop usually is around 1100 FPS. I've seen it as high as about 1115 and as low as about 1060 or 1070FPS. Normal shot to shot variations can change velocities substantially. Leaving a loaded round in a hot chamber can easily transform a sub-sonic round to sonic. In many loads, each one tenth of a grain of powder can change the velocity 30-40 FPS which is normally not a big deal. If you want to load very uniform ammunition to just below the speed of sound, I strongly suggest an electronic powder measure and the weighing of 10 charges to obtain your average actual charge weight. Many powder measures are not very accurate with these small charges. We can furnish extremely accurate measures at minimal cost. All of the above hand loading factors applying to all small cartridge case ammunition and are really nothing new.

The range of powders useful in the 300 Whisper® is very wide, ranging in burning speed from Accurate Arms #2 through 11-322. In general, powder in the burning range of AA #9, H-i 10, WW 296, AA 1680 give excellent accuracy and velocities with practically all bullet weights and velocity ranges. In subsonic loads powders that burn faster than AA#9 should not be used in AR-15s.

The 300 Whisper®-VS-OVER-VS-UNDER penetration: Particularly in the urban role the 7.62 x 51(308) has given excessive penetration in numerous instances where a 300 Whisper® would have accomplished the job silently, effortlessly and without endangering the lives of others by use of a needlessly powerful weapon. The 5.56 x 45 (223) has given over penetration in some buildings while falling on glass, automobiles and other objects with the same ammunition. The 300 Whisper® addresses many of these problems successfully. Those with extensive experience in attempting to penetrate automobile bodies will recognize almost anything short of a 50 BMG will have the occasional failure to get through some automobile on some shots.


A 300 and 338 Whisper® sub-machine gun has been developed which renders obsolete any "pistol" caliber sub-gun. Accuracy and control are simply unmatched by any other subgun. A pistol has also been developed. Both can be suppressed. The 6.5 Whisper® (85 through 160 grain bullets) and the 7MM Whisper® (100 through 185-grain bullets) are ready for sale. Both work in AR-15/M-16 as well as other type guns. The 338 Whisper® (175-300 grain bullets) is extremely accurate and may be had in Contenders or "308" bolt action rifles can be converted to it. A switch barrel 338 Whisper® .308/7/08 can also be had. The 458 Whisper® uses all normal 458 bullets plus 560 and 600-grain low-drag bullets for tremendous downrange performance. The 500 Whisper® is simply the most powerful subsonic round in existence. Both of these can be had in bolt actions or Ruger #1 rifles. Numerous other very accurate sub-sonic rounds utilizing heavy ballistically efficient bullets have been developed. Those with special needs are invited to inquire.

SSK also makes a wide array of custom rifles, handguns and suppressors ranging from 22 rimfire through 50 caliber which provide unequaled accuracy in subsonic usage. Click HERE to go to SSK Industries web page!

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This page was last updated 03/07/06

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