.300 Whisper by Hornady, AMAX Subsonic, One Cartridge not a Box.
For more information please see below.
Please click on the picture for more detail.
Please Note: On the above picture, the picture on right for comparison: Left is .300 Whisper and Right is .221 Remington Fireball.
One Cartridge not a box: .300 Whisper by factory production by Hornady using new Horandy brass cases with “HORNADY .300 WHISPER” Head-Stamp and loaded with a 208 grain AMAX projectile. “SUBSONIC” only 1,000 Feet per Second.
The history of the .300 Whisper Cartridge:
The 300 Whisper was developed as a wildcat cartridge by J.D. Jones of SSK Industries for the Thompson/Center Contender single shot pistol or rifle.
It was made by necking out the .221 Remington Fireball from .22 caliber to .300 caliber,which also reduces the case neck angle from 29 degrees to 23 degrees.
It was later produced by the Cor-Bon Company, and in 2013 by the Hornady Company for the AR-15 platform for tactical entry operations by military & police.
Although the .300 Blackout (a standardized version of the 300 Whisper) and .300 Whisper are very similar, you should not fire a .300 Blackout in a firearm cambered for .300 Whisper as they may have slight variations in chamber dimensions , which could lead to unsafe high preserves. I can’t speak for the Hornady production.