Whispers®: A wide range of calibers encompass the ‘Whisper®’ series of cartridges. A “Whisper®” cartridge must be capable of sub-sonic extreme accuracy with very heavy bullets for its caliber; i.e. 240 grains in 30, as well as moderate to high velocity while maintaining excellent accuracy with light bullets for the caliber; i.e. 125 at 2300 FPS in 30. The 300 Whisper® was the first of the series, and, contrary to what you may have read about it, the fact of the matter is the cartridge was designed as a multi-purpose cartridge from the beginning. Its design parameters, in addition to the ballistics quoted above, were that it must be capable of being used in the AR-15/M-16 family of rifles, Contenders and bolt action rifles as well as being easily suppressed. I know that because I invented it. It revolutionized the tactical suppressed sub-sonic field in controllability in full auto, power and accuracy. It has been very successful and has gained wide acceptance as a hunting round for mid-size game, such as deer, and has probably taken a wider variety of game than any other handgun cartridge in the same time span. Due to its small case capacity, its recoil is very mild. One Whisper® series from 6 mm, 6.5 mm, 7mm, 300 and 338 is based on the 221 fireball case. Another series is based on the 7 BR case in 338, 375 and 416 caliber to convert 308 case head size actions. Another used the 460 Weatherby case for 50 caliber conversions to 300 Win Mag case head size rifles. Others use rimmed cases, such as the 50-70-750, for use in single shots.
Sub sonic 820 grain spotter tracer from a 510 Whisper® impacting steel at long range.
10 shot full auto burst close up of bolt, feeding, ejection in slow motion.
18 shot full auto burst from M-16 300 Whisper® ejection pattern.