300 Whisper

Can anyone tell me anything about the cartridge shown. H/s is R . P 221 REM. The bullet is .30 and the case length 1.35 inches.


It’s a 300 Whisper. A proprietary cartridge of J D Jones (SKS Industries). It’s intended to shoot heavy, high BC bullets, at sub-sonic velocities out of supressed weapons. (“Proprietary” is a high class name for a wildcat.)

Shooters, being who they are, use it for other purposes and you can also find variations of it, primarily case length, parent case, and bullet weight. And since velocity is king, they will try to push bullets as fast as they can from that tiny case, in complete disregard of its original intended purpose.



Thanks very much for all the information.

kind regards


Those who don’t want to pay J.D. Jones’ tariff also call it the .300/221 and .300 Fireball.

Indeed we do. I have have a T/C Contender with a 10" barrel in this caliber, which I use with (typically) 180 grain bullets for hunting whitetail deer. A suprisingly versitile round.