| .300 Whisper | |
| Type: | Rifle |
| Origin: | United States |
| Design Date: | c. 1990 |
| Parent: | .221 Fireball/.223 Remington |
| Case Type: | Rimless, Bottleneck |
| Is Si Specs: | yes |
| Bullet: | 7.82 |
| Neck: | 8.46 |
| Shoulder: | 9.14 |
| Base: | 9.54 |
| Rim Dia: | 9.60 |
| Rim Thick: | 1.14 |
| Case Length: | 34.90 |
| Length: | 57.00 |
| Rifling: | 203 mm (1 in 8 in) |
| Primer: | Small rifle |
| Bw2: | 220 |
| Btype2: | JHP |
| Vel2: | 1040 |
| En2: | 529 |
| Test Barrel Length: | 16 in |
| Balsrc: | CIP specifications COR-BON Ammunition |
The .300 Whisper (7.82x34mm) is a CIP standard[1] 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 bullets at supersonic velocities as well as heavier bullets (200–250 grains) at subsonic velocities.
.300 Whisper is also sometimes known as .300 Fireball or .300-221, but the .300 Whisper is a CIP cartridge and other names are generally known as wildcat cartridges. When compared to .300 AAC Blackout Steve Johnson’s article in American Hunter sums it up best:
Given the fact that major manufacturers such as Hornady are building ammunition headstamped .300 Whisper and recommending it for use in either platform—in addition to producing reloading dies that are marked “300 Whisper/Blackout” and Smith & Wesson stamps the barrel of its M&P-15 Whisper barrels with: “300 Whisper/300 AAC Blackout” it is safe to say that differences are minimal.[2]
The CIP has standards for both .300 AAC Blackout and .300 Whisper defined. The two are very similar in these definitions.
The .300 Whisper was originally based on the .221 Fireball case necked up to .30 caliber. However, reloaders have found the .223 Remington or 5.56×45mm NATO works well when shortened and resized to .30 caliber. Firing in the .300 Whisper chamber results in a slightly sharper shoulder. Magnum pistol powders such as H110 work well for supersonic loads. Sierra 240 grain (16 g) jacketed bullets work well if the barrel has a 1:8 twist. Barrels with a 1:10 twist will stabilize 220 grain (14 g) bullets at subsonic speeds. 125 grain (8 g) bullets will reach 2,400 ft/s (730 m/s).
There are a few points regarding the utility of the .300 Whisper:
In addition to special applications in suppressed firearms, the .300 Whisper has become popular with metallic silhouette shooters due to its low recoil, good long range performance, and high accuracy.
SSK Industries has a registration for the wordmark "Whisper" (reg. no. 1898840) in class 13 (ammunition).[3] 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 identical or highly similar cartridges. These include ".300 warrior carbine", ".300 Fireball" or ".300-221", both based on the .221 Fireball parent case. The .300 AAC Blackout has succeeded as a commercial cartridge while the Whisper never achieved wide acceptance.