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300 AAC Blackout

300 AAC

In 2011, SAAMI finally standardized the 300 Blackout. This is nothing more than the 300 Whisper loaded to higher pressure to launch relatively heavy 30-caliber bullets at about 1500 fps from the AR-15 platform. As such, it generates similar energy as the 223 Rem when loaded to the same pressure and using the same length barrel. But, with the right bullet, it can be far more effective as a fight stopper.

While efficient bullets can hold velocity well, trajectory limitations of a projectile launched at less than half the velocity of a typical 223 bullet limits effective use for most situations to relatively short range.

Originally developed by JD Jones at SSK as a proprietary sub-sonic cartridge he called the 300 Whisper, he chambered it in the Thompson Contender single-shot gun in 1992. This case is based upon the 222 family.

 


 

Just like the first cases Jones made for the 300 Whisper, cases for 300 ACC Blackout are a shortened version of the ubiquitous and handy 223 cases. Case length is just a little less than case length of the 221 Fireball.

Jones’s goal was to create a 30-caliber round that would launch the Sierra 220-grain hollow-point boat-tail bullet at about 1050 fps from a pistol-length barrel using a very small charge of a very fast propellant without generating high pressure or significant propellant-gas volume. This allowed efficient silencing. He achieved his goal in spades (see below).

Serendipitously, or not (again, see below), the resulting round happens to fall within the usable length for the AR-15 platform. The resulting round can also be loaded to achieve significant ballistics and work in the AR platform when launching relatively heavy 30-caliber bullets at super-sonic velocities while generating normal 223 pressure.

Interesting historical note: I was honored to meet JD Jones shortly after he finalized the design of the 300 Whisper. We were invited to an industry varmint hunt with Cor-Bon and Dakota Arms. Of course, JD brought along his Contender 300 Whisper to show it off. Cor-Bon happened to be developing a sub-sonic factory-load at that time.

We shot the Contender with preliminary Cor-Bon ammunition loaded with the 220-grain Sierra HPBT bullet. With the small and efficient suppressor screwed on the barrel, the gun was so quiet when fired that you could only hear the gases venting if it was dead quiet and you had good hearing; if someone was talking in a normal voice and standing within ten feet or so, that conversation entirely overwhelmed the sound of the gas venting and the shooter could not hear that dull whoosh sound.

Conversely, the sound of the gun being dry-fired was obvious to everyone as a relatively loud click when the hammer hit and rebounded from the frame; when the gun was loaded, the hammer hit the firing pin, which hit the primer, which fired and pushed back on the hammer and prevented it from hitting the frame. Mechanically, the firing gun made no perceptible noise.

The ballistician at Cor-Bon had an incident while we were field-testing the Contender and he was working up a load for it. He did not realize one of the two Dakota rifles on the shooting bench was chambered in 223 and managed to chamber a 300 Whisper round in it. The bullet used and the seating depth created a situation where the ogive of the bullet happened to perfectly engage the chamber shoulder and provide artificial headspace control. When he fired the shot, he heard nothing over the sound of the fan and he felt nothing.

The case head vaporized but the fantastically efficient gas-control safety features of the Dakota (improved) M-70 Winchester replica Don Allen had designed, prevented any of the gas or brass from reaching him. The bullet was lodged about halfway down the bore and was easily removed. It was the most beautiful 220-grain 22-caliber bullet you ever saw!

It is safe to say such an incident in many guns would result in catastrophic damage to the gun, shooter, and bystanders. Use due caution to avoid repeating this fiasco, an event that could well end in something far more serious than mere embarrassment!

The heritage of this case dates to the 38 Colt cartridge of the 1860s and before that with the 1839 introduction of the 36 Colt Paterson cap-and-ball Revolver.


The text associated with the cartridge description reflects opinions and conclusions of the author, M.L. (Mic) McPherson. Lee Precision and its employees do not necessarily either agree or disagree with any of his comments. We present these with due deference to his recognized expertise in the firearms field. His acumen extends to handloading and all aspects of ballistics - internal, external, and terminal.
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