The .300 Whisper
By Chuck Hawks
There are so many factory loaded rifle and pistol cartridges today that many of them are redundant. There is no meaningful performance difference between the .45 ACP, for example, and the .45 GAP, or the .300 Rem. SAUM and the .300 WSM.
But wildcat cartridge designers cannot be discouraged. One of the interesting niche developments in handgun hunting and silhouette cartridges is the .300 Whisper. It is the result of J.D Jones' experiments in the area of small capacity cases with larger diameter bullets in suppressed firearms. Needless to say, this is not an area of broad interest to hunters and recreational shooters.
The .300 Whisper is a rimless, bottleneck cartridge based on the .221 Fireball case simply necked-up to accept .308" diameter bullets. It has recreational application primarily in the area of handgun silhouette competition, and Thompson/Center and SSK offer barrels in .300 Whisper.
You might think from its name that the .300 Whisper is subsonic, but that is not the case. The .300 Whisper drives even 180-190 grain bullets at supersonic speeds, but its muzzle blast is relatively innocuous.
.300 Whisper cartridge dimensions are as follows: .378" rim diameter, .376" head diameter, .361" shoulder diameter, .335" neck diameter, 1.40" case length, and 2.260" maximum cartridge overall length. The miniscule shoulder has a 23 degree angle, the same as the .221 parent case.
The sixth edition of the Hornady Handbook of Cartridge Reloading lists loads for bullet weights from 110 grains to 190 grains. It shows that a minimum charge of 14.4 grains of IMR 4227 powder behind a 150 grain Hornady bullet gives a MV of 1500 fps from the 10" barrel of a Contender pistol. A maximum charge of 17.4 grains of IMR 4227 gives a MV of 1800 fps. These loads were developed in a T/C Contender pistol and used Remington cases and Federal 205 primers. That is pretty impressive performance for such a small case fired in a 10" pistol barrel.
Copyright 2006, 2014 by Chuck Hawks. All rights reserved.