300 Whisper

The .300 Whisper is a cartridge in the Whisper family developed in the early 1990s by J.D. Jones of SSK Industries. It was developed as a multi-purpose cartridge for super and subsonic application. Originally it was based on the .221 fireball case necked up to .30 caliber however reloaders eventually found that .223 and 5.56 NATO brass works well.