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Shades of Gray: .300 Whisper & .300 AAC Blackout

There is a great deal of confusion regarding these two similar cartridges with different names. But how did they develop, and how similar are they?


Very few things in life are black-and-white, and things are seldom as simple as they appear. The truth usually lies somewhere in the middle. Okay, I am out of clichés now. But those catch phrases apply to the buzz, misconceptions and misunderstandings surrounding the .300 Whisper and .300 AAC Blackout cartridges—and to the guns chambered for them. There is a great deal of consumer confusion between the .300 Whisper and the .300 AAC Blackout. Are they the same? Are they different? If I buy a .300 Blackout can I use .300 Whisper ammunition in it safely? What about the .300 Whisper I’ve had since the 1990s? Is it safe with .300 Blackout ammunition? What about the other .30-.221 wildcats?

Here are two things we know for sure. The .300 AAC Blackout is a Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) standard cartridge. The .300 Whisper is a Commission Internationale Permanente pour l’Epreuve des Armes a’ Feu Portatives (CIP) standard cartridge. Rumor has it that the .300 AAC Blackout will likely become a CIP standard cartridge, as CIP allows duplicate cartridges with different names, which SAAMI does not. Please refer to schematics on p. 92 to see for yourself.

The .221 Fireball was developed in 1963 by Remington for use in the predecessor to the XP-100 pistol. Again something we know. It is unknown who first necked up the .221 Fireball to .30 cal., but the purpose was most likely metallic silhouette shooting, which was very popular at the time.

Two other things that we know: The .300 Whisper was developed, documented and trademark-
registered in 1992 by J.D. Jones. The .300 AAC Blackout was developed, documented and presented to SAAMI by Advanced Armament Corporation in 2009. Hornady Mfg. Co.—a SAAMI member company—recommends its .300 Whisper ammunition in firearms chambered for either .300 Whisper or .300 AAC Blackout. Confused yet?

Hornady is one of the most respected ammunition manufacturers in the world and, as I am a former Hornady employee, I know that it wouldn’t recommend such a practice unless it had thoroughly tested for safety, reliability and function. When Hornady says its ammunition is good to go in the .300 Whisper and .300 AAC Blackout, you can take that to the bank.

J.D. Jones is likely responsible for the vast majority of the work in the field of subsonic ballistics during the past 20-plus years, and he is unofficially considered by many the father of modern subsonic ballistics. Jones owns SSK Industries and, among other accomplishments, developed the series of cartridges with both “JDJ” and “Whisper” designations. Jones developed “Whisper” cartridges from 6 mm to .50 cal. and everything in between. The .300 Whisper was the first in the series, developed in 1992.

My first experience with the .300 Whisper came when I was developing load data for the 5th Edition Hornady Handbook of Cartridge Reloading more than a decade ago. I was impressed enough to purchase an SSK barrel in .300 Whisper for my T/C Contender. It had the ability to shoot projectiles from 0.308" pistol bullets all the way up to heavy match rifle bullets, such as the Sierra 240-gr. BTHP MatchKing and later the 208-gr. A-MAX, which I have used to take game including whitetail deer. Jones explained that the .300 Whisper really shined when it was chambered in M16/AR-15 platform rifles, especially short-barreled rifles, as it acts more like a pistol cartridge than a rifle cartridge.

In 2009, word spread that AAC was bringing out a cartridge similar to the .300 Whisper and calling it the .300 Blackout. Enter the controversy. I called on Robert Silvers, director of research and development for AAC. He has been willing to share drawings, specifications, etc., and even forwarded the SAAMI-approved chamber reamer drawing of the .300 AAC Blackout reprinted below. Silvers and AAC have been forthcoming and helpful with any and all information about the .300 Blackout. If I had not had the background that I did with the .300 Whisper, nor a ringside seat inside the industry as a Hornady employee, I would have readily assumed that the .300 AAC Blackout is a completely different cartridge than the .300 Whisper. A large percentage of firearm enthusiasts believe that is the case, and it simply is not.

Why the .300 Whisper and the .300 AAC Blackout? To answer that I interviewed the two men responsible for the two most popular versions of the .30-.221 Fireball—SSK’s Jones and AAC’s Silvers. According to Jones, the .300 Whisper was developed in the Fall of 1992 with the first-use copyright on Nov. 12, 1992. The Whisper’s development “Simply boils down to my interest in developing ‘new’ cartridges and applications. Up to the point when I invented the .300 Whisper I don’t know of anyone who gave much thought to accuracy in a subsonic, silenced [arm] in this country,” stated Jones. “To be successful I thought the cartridge had to have both heavy-bullet, subsonic silenced and light-bullet, moderately high-velocity capabilities; be useful in the M16, single-shots, [and] bolt-actions; easily silenced with recreational shooting such as metallic silhouette and moderate big-game capabilities—such as pigs and deer—with exceptionally low recoil and decent accuracy. The .221 Fireball cartridge case was the right length, readily available and easily neck expanded to .30 caliber. The .223 case was looked at and found to present many problems due to its many variations in capacity, wall dimensions giving unacceptable neck wall thickness variations, in addition to being a tough trim job. Expanding neck dimensions to accommodate all of these variations would result in sloppy neck dimensions and in accuracy and sizing problems. An overly thick neck can allow a semi-automatic to chamber a round almost fully but not enough to fire.”

As to the development of the .300 Blackout, Silvers said: “We started development in 2009, but most of the work was done in 2010. A military customer wanted a way to be able to shoot .30-cal. bullets from an M4 platform while using normal bolts and magazines, and without losing the full 30-round capacity of standard magazines. They also wanted a source for ammunition made to their specs. We could not have just used .300-.221 or .300 Whisper because Remington is a SAAMI company, and will only load ammunition that is a SAAMI-standard cartridge. We had to take the .300-221 wildcat concept, determine the final specs for it, and submit it to SAAMI. We did that, and called it the .300 AAC Blackout (.300 BLK).”

Reamer/Chamber Drawings (Click to Enlarge)


But how similar are the two cartridges? Is .300 Blackout ammunition compatible with guns chambered for .300 Whisper and vice-versa? Silver replied: “Hornady .300 Whisper ammo, according to Hornady, has been specifically tested to be within SAAMI specifications for .300 AAC Blackout. If you shoot .300 BLK ammo in chambers that have a shorter or tighter throat, pressures will go up—perhaps above SAAMI maximums—so it is not OK to mix ammo.”

Jones said: “It is the same case—I don’t know why not. Same chamber works, same loading dies work. The S&W guns function fine with Hornady ammo in subsonic or high velocity. I killed two deer with Hornady [.300 Whisper ammunition] and although I would prefer a bit heavier bullet, both deer were cleanly killed.”

I wanted to see for myself what the differences between the two cartridges were in a real-world scenario. I approached Smith & Wesson, Freedom Group and SSK for test rifles chambered in .300 Whisper and/or .300 BLK. I contacted Cor-Bon, Hornady, Remington and purchased some Atlanta Arms & Ammunition cartridges for testing. I tested more than 600 rounds of ammunition from the aforementioned manufacturers for accuracy, velocity, consistency, function and overall performance. I also tested some handloads provided by SSK Industries.

All of the information is presented in the tables and schematics for the reader to make his or her own conclusions. I can tell you, based on a great deal of time in a ballistics lab, if you fire the same ammunition in two different guns and if one of those guns is tighter in the chamber, throat and/or barrel, the pressure and velocity will be higher in the tighter gun, exactly as Silvers stated above.

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20 Responses to Shades of Gray: .300 Whisper & .300 AAC Blackout

Chris wrote:
January 10, 2014

@Mike The SSK has an adjustable gas system, which they adjusted during testing. The others do not. It's not that there is anything 'wrong' with the S&W and Bushmaster, it is that the SSK allows for adjustments to these widely-varying loads.

Mike wrote:
December 26, 2013

What I find most telling about this article is in the function columns of the Shooting Results graphs. The S&W and Bushmaster both have failures to function. The SSK had none. Enough said.

Eric wrote:
September 30, 2013

Bob, I believe hornady has load info for 150 grain bullets in their newest manual. that is what I am hearing anyway. I just ordered 400 150grain fmj-bt from natchez so Im sure hoping that is true.

Bob wrote:
September 25, 2013

I would like to know if anyone has some hand loads in the 150gr or + range that works

tuna wrote:
April 22, 2013

The info I received from Corbon regarding their 300 Whisper ammo. It is perfectly safe to use our 300 Whisper in your 300 BLK rifle. Thanks, Michael Shovel Vice President/Public and Media Relations COR-BON/Glaser

X8ico wrote:
April 06, 2013

In Indiana the law about handgun hunting for deer is .243 diameter or larger. For deer rifles the law is .357 diameter or larger with case length 1.16 minimum to 1.80 length max. There are many .358 wildcats being made for deer hunting in Indiana with necked cases shooting around 2850 fps that are within the Indiana law...

Hardcoredeerhunter wrote:
April 03, 2013

Davis. Where did you sumise that this cartridge is legal to use for pistol deer hunting in Indiana. The law clearly specifies staright walled cases. The 300 Blackout is not a straight walled case.It is necked down.

Pete Towers wrote:
March 13, 2013

Jamison Brass and Ammunition has makes the brass and loads 300BLK. They are currently taking orders. or you can call directly 605-791-1974

Davis wrote:
March 10, 2013

300 AAC Blackout Used for 1st Place Win at MultiGun Nationals. Also legal for pistol deer hunting in Indiana

lee wrote:
February 22, 2013

I have hard time to hunt for these ammo, help me where to buy please

Roy wrote:
January 13, 2013

It appears the same set of dies can be used to reload either 300 Blk or 300 Whisper.

blAACkout wrote:
January 11, 2013

So you can or cannot shoot 300 whisper in a 300 blackout without damage? What other rounds can be safely fired from a 300 blackout without modification?

Bob wrote:
January 08, 2013

Because you can

Wolfsbane wrote:
November 28, 2012

Call these two rounds what they really are. A 7.62 Tokarev Magnum.

Carl Laury wrote:
November 17, 2012

I just finished my first AR build and I chose the .300AAC as the cartridge to use. This article is right on time as I now don't have to skip buying rounds if the store is out of the AAC but has Whisper in stock. Thanks

Mike in PA wrote:
November 15, 2012

@Dan in Austin: Some of the various flavors of 264LBC/6.5 Grendel also use a 7.62x39 bolt and I am not aware of widespread bolts breaking. That having been said, I have read of reliability issues with the 7.62x39 in ARs due to the tapered case WRT feeding. I too would love an upper in the .300 Blackout/Whisper.

Dan in Austin wrote:
November 15, 2012

7.62x39 is a problem in AR type guns due to the tapered case. Opening up the bolt to allow the round also weakens it, which is why you see so many of them break in ar's converted to 7.62x39

Mouse wrote:
November 14, 2012

Interesting. But why not the battle-proven 7.62x39?

mater wrote:
November 14, 2012

while i have been impressed with jones's work in cartridge developement this one has me wondering simply why? and the blackout whywhywhy????

Michel wrote:
November 14, 2012

Thanks for the clarifications! I've been lusting a Whisper for quite a few years... Now it's nice to know there are more options out there!