Over the last several years many new calibers have been introduced to the AR-type platform; from the .204 Ruger, 6.8mm Rem SPC, 6.5 Grendel, 7.62x39mm, 5.45x39mm, 5.7mm, .450 Bushmaster, .458 SOCOM, .50 Beauwolf and .499 LWR.  These are just for the AR-15 platform; there is a whole other array to the AR-10.  Of all those mentioned, the only one who has really done well is the 6.8mm Rem SPC.  There are several manufacturers of rifles as well as ammunition.  As of this writing this author could not find any ammunition available for the .458 SOCOM, .50 Beowulf or the .499 LWR.  Nevertheless, around 1991 a new round was developed by JD Jones of SSK Industries that would prove versatile and offer tactical advantage, the 300 Whisper.  In November of 1992, he trademarked the name.

The first M16/M4 rifle to properly be adapted to the 7.62x39mm caliber cartridge was manufactured in small numbers for a special operations requirement: this is known as the SR-47. Knowing the only reliable way to feed the rifle was to use the AK47 magazine, which is just what Reed Knight did. This rifle never went into production though Rock River Arms recently introduced the LAR-47 which is a M4 with receivers modified to accept the AK47 magazine.

During research for this article, JD Jones was interviewed to get the backdrop on the development of the 300 Whisper:

“I first licensed Thompson Center (T/C) to use it and they put it into the Contender and it became quite popular in the Handgun Metallic Silhouette competition for years.  T/C uses a 1-in-10 twist, which is not good for sub-sonic with heavy bullets.  Initially in the AR we used a single port gas system, about what S & W is now using and found with heavy sub-sonic bullets, 1680 powder would function it (although quite dirty) and high velocity ammo also had a small window of functioning without working the gun too hard.  The SSK adjustable gas system solves the problems of functioning with a quite wide window of proper functioning with a wide range of powders and bullet weights.  This system has an L, for generally low velocity ammo, and H for high velocity ammo and in between those settings the gas is shut off.  For example we have loaded 220 sub-sonic (1,040 fps) and 220 HV (1,400 fps) from a 10-inch M16 for some people.  In a non-adjustable gas system the port pressure of the HV load would be quite high giving excessive bolt velocity with a single non-adjustable system if the sub-sonic was to function reliably.  With our system the HV will work the gun OK but also too violently for my taste.  We’ve used a 6 to 12 inch twist rate and found 8 or 7 inches to be the most versatile.  It is probably the most copied cartridge in existence today.  It was CIP dimensioned many years ago and commercially manufactured in Europe for about 15 years.  It has been called the 300/221; 300 Hush, 300 Murmur (France) 300 fireball, etc., and the latest 300 Blackout.  Over the years there have been many problems with functioning of ARs with single non adjustable gas ports but the chamber dimensions have all seemed pretty close – close enough to use the 300 Whisper dies and basic data.  In 1992, the practical way to make the cases was simply to open the 221 case to 30 cal. – anyone could do that with the dies we supplied.  223/5.56 case wall thicknesses varies a lot; however later we had hundreds of thousands of cases made from primarily LC military brass with an operation to give proper neck wall thickness.  Inquires were made to the majors to make brass.  One asked for an order for 1 million rounds loaded ammo and they “would consider it” and Pete Pi told me the other just turned it down flat.  I think any chamber is capable of having problems with cases made from some 5.56 or 223 brass due to ending up with excessively thick neck wall thickness.”

Shown from left to right are the 5.56x45mm M855A1, 6.8mm Rem SPC, 7.62x39mm and the .300 AAC Blackout cartridges.

The 300 Whisper was never submitted for acceptance by SAMMI.  What this means is that there was never an industry standard on cartridge case dimensions, chamber dimensions of loading specifications.  This makes it difficult for an ammunition producer to make ammunition that will work properly in any given firearm.  Ammunition has been manufactured by Hornady and Corbon, however, a majority of the ammunition has been hand loaded with cartridge cases manufactured from the .221 Rem parent case.

Continuing with JD Jones’s proven concept, Advanced Armament Corporation went to work with Remington and the backing of the Freedom Group family of companies to bring to market their 300 AAC Blackout cartridge.  The main difference is that you can fire a 300 Whisper safely in a 300 Blackout chamber but not the other way around.  Sort of like not firing a 5.56mm cartridge in a .223 Rem chamber. Higher pressures can result from minor dimensional differences.  AAC does not recommend any 300 Whisper ammunition unless it was manufactured by Hornady due to Hornady adhering to the data for both making a compatible round.  Ammunition is readily available for the 300 Blackout in everything from inexpensive Remington UMC brand target ammo to 125 grain supersonic defense/hunting ammunition to 220 grain subsonic ammunition designed for use with a sound suppressor.  Ammunition has been made by BVAC, Barnes, Corbon, Federal, Silver State Armory, Remington and PNW Arms.

Shown is JD Jones in 1993 firing the first subsonic 300 Whisper round. Notice the short barrel. This was the beginning of what would eventually yield the 300 Blackout.

What makes this cartridge stand out?  For many years weapons manufacturers in the AR business wanted to chamber their rifles in the 7.62x39mm caliber.  There have always been detractors to the 5.56mm caliber.  Companies such as Colt, Knight’s Armament, Rock River Arms and ArmaLite are just a few of the companies to chamber their AR-platform rifles in 7.62x39mm.  All of them came up with the same conclusion; there has never been a proper magazine that would properly fit in the AR-platform magazine well.  The taper on the 7.62x39mm cartridge case is just too steep to have the column line up in a straight top AR-type magazine, so this is the cause of the reliability problems with AR-type rifles chambered in the 7.62x39mm cartridge.  Reed Knight fixed that on his SR47 when he adapted the rifle to the AK47 magazine.  This was the only way to truly fix the problem but it is costly and requires an entirely different lower receiver.  Although KAC pioneered this design, they never put it into production.  This would be revisited by Rock River Arms with their LAR-47 Delta Carbine.  As of this writing though, it will not be available till mid to late next year.  The taper on the cartridge case requires a curved magazine.  Many felt the ballistics of the 7.62×39 were excellent for an assault rifle but did not like the AK47 design and lack thereof in the accuracy and human engineering departments.  The 300 Blackout duplicates if not slightly improve upon the 7.62x39mm cartridge.  Also, the Blackout uses a 0.308 diameter projectile which is one of the most popular in the world with many selections of projectiles, as opposed to the 0.311 of the 7.62×39, which has very little options of type and weight.  The 300 Blackout enables weights from supersonic 110-175 grain to subsonic 200 to 250 grain, making it an extremely versatile cartridge for use with and without a sound suppressor.  The supersonic ballistics are equivalent to the venerable 7.62x39mm, and suppressed can be as quiet as an MP5-SD.

Shown is the destruction caused by a Barnes TTSX 110gr projectile fired out of a 300 Blackout at 100 meters.

The 300 Blackout cartridge fits in the standard AR magazine without any loss of the original 30 round capacity.  The standard bolt and barrel extension is used as well.  The only difference is the barrel itself.  This not only makes for easy logistical support for potential military use of the caliber, but you can pull spare parts from existing .223/5.56mm rifles.  The sample rifle has been tested with GI aluminum magazines, H&K high reliability mags, Lancer AWM and Magpul PMags.

In November of 2011, AAC received SAMMI approval on the 300 Blackout.  Since then more than 150 manufactures have come out with complete rifles, upper receivers, barrels, ammunition, or other products in this caliber.  Due to being SAAMI registered and so freely usable by anyone without a license, many companies were able to support the project and with the backing of Freedom Group the Blackout was a sure success.  Significant amounts of time and money were put into JD’s 300 Whisper concept to get it the recognition and acceptance that it so deserved, but now officially standardized as the AAC 300 Blackout.

Of all of the rounds tested in this exciting caliber the most impressive was the Barnes 110gr TAC-TX. This is a solid copper barrier bullet with a polymer insert in the tip.

AAC’s Director of Research and Development had a few things to say about why the cartridge is so popular: “There are three things that made all of the difference.  First was getting industry acceptance through SAAMI – thus allowing anyone to make guns or ammunition that interchanges, and without having to pay royalties.  The second was making high quality but low cost ammunition widely available – which we did with the Remington 115 grain UMC – and without compromise as it actually has premium features such as brass with NATO-like hardness, water proof primers, and a bullet constructed as an open-tip match – but with the nose struck closed to uniform the ballistic coefficient.  The third was that we cracked the code for making the rifles and ammunition reliable without requiring an adjustable gas block.  The military made this a requirement – as one does not want to be caught on the incorrect gas block setting and have a malfunction, or be forced to switch settings on the fly.  Eliminating the need for adjustments was a success, and while using an AAC rifle with its fixed gas system, one can go from subsonic unsuppressed to supersonic suppressed and all four configurations of firing will be within the 700 to 950 rpm cyclic rate specs of a Colt M4.  We were able to do this by designing the guns and ammunition as a team between Remington, Barnes, and AAC – and other makers are following suit, so there are a wide range of choices.”

Test ammunition provided for this test consisted of Remington loads including the UMC 115 CTFB, 125 grain OTM, 125 grain Accutip and the 220 grain OTM (subsonic).  The UMC ammunition sells for $11.99 a box making this caliber very reasonably priced for the shooters, as opposed to some of the other calibers that start at $22 and go up from there.  In fact, the 300 AAC Blackout ammunition is less expensive than .30-30 Winchester ammunition.  As of this writing the only calibers other than 5.56mm in this platform that are easily available and reasonably priced are the 6.8mm Rem SPC and the 300 Blackout – and 6.8mm Rem SPC is on average 40% more expensive than 300 Blackout.  Both 6.8mm Rem SPC and 300 Blackout have full lines by Remington including inexpensive UMC target ammunition.  The most impressive load for the 300 Blackout is the Barnes 110 grain TAC-TX.  All-copper TAC-TX, which are not only blind barrier, will expand to about 60 caliber at 300 yards even when shot from a 9-inch barrel.

Shown is how the T&E AAC 300 Blackout upper receiver assembly was received. The upper receiver with a KAC URX-III, custom bolt carrier group & sound suppressor.

During testing, there were three different weapon systems tested with this new and exciting caliber.  The first came from the originator of the 300 Blackout cartridge as we know it, AAC as a complete upper receiver.  The second was a complete upper receiver manufactured from DS Arms, Inc., and lastly the Lewis Machine & Tool LM8 MRP CQB with the newly introduced 300 Whisper/300 Blackout barrel assembly.

The AAC product has a 16-inch, 1/7 inch twist barrel and comes with their flash suppressor mount that accepts their optional sound suppressor.  The upper receiver comes with a carbine length direct-impingement gas system and a Knight’s Armament Mid-Length URX forearm grip/quad rail.  The front sight is integral to the hand guard and folds into a front section of rail.  The upper receiver has a forward assist and an ejection port dust cover.  This is a standard M4 upper receiver with extended feed ramps cut into the receiver extension and upper receiver.  The bolt carrier is a custom AAC unit that has a nickel boron-type finish and a sleek look to it.  AAC states that its thicker, duel-layer coating provides far more corrosion resistance than the way NiB is typically applied as a single very thin layer.  Forward assist notches sit back further and there is an AAC emblem laser engraved on the carrier.  The extractor has a green rubber “O” ring that provides more extractor force to enhance reliability, and is made of a special material designed not to bind up even in -40F temperatures.  The upper receiver was also mounted on an LMT Defender lower receiver, and tested in both fully automatic, as well as semiautomatic.

As received from DS Arms, this 300 Blackout upper receiver assembly did not come with a bolt carrier group or charging handle. This is a cost effective way to shoot this caliber.

With full power supersonic ammunition the AAC upper receiver functioned flawlessly.  More than 300 rounds of Remington UMC 115 grain ammunition and 300 rounds of Barnes 110 grain TAC-TX were fired.  The rifle was easily controlled even in fully automatic, and kept 3-5 round bursts with no difficulty in the center of a silhouette target at 15 meters.  Certainly the 300 Blackout was easier to shoot than an AK47/AKM firing the nearly identical cartridge.  Also tested with the rifle were standard aluminum GI magazines, PMag, Lancer L5 AWM and H&K high reliability magazines.  Both 20- and 30-round configurations were all tested as well.  Accuracy was very impressive averaging 1 to 1.5 inches at 100 yards.  The MSRP for the complete AAC upper with the KAC URX-III handguard is $1,080.

The upper receiver provided by DS Arms utilized a 16 inch 1/8 inch twist heavy 416 stainless steel barrel.  The forged front sight base is pinned in place.  At the end of the muzzle is a Trident flash suppressor.  The receiver is a Mil-Spec 7075 T6 receiver with a forward assist, ejection port dust cover and fired cartridge case deflector.  The barrel extension has extended feed ramps.  No charging handle or bolt carrier group comes included with the unit, so an LMT enhanced bolt and carrier were used, along with an LMT Tactical charging handle.  This upper receiver was placed on an LMT Guardian selective fire lower receiver with an H buffer.  More than 300 rounds again were placed through this rifle.  Remington 125 grain and Barnes 110 grain TAC-TX were fired. Both Hornady 208 grain and Remington 220 grain subsonic ammunition were also fired.  There were no malfunctions of any type of ammunition in either semi-auto only or fully automatic fire.  This upper had no issues with cycling subsonic ammunition without a sound suppressor on it.  Accuracy was very respectable with 1.5 to 2 inches at 100 yards.  The optic used on this rifle was an AimPoint Comp 4S with the 3x magnifier.  This upper receiver sells for an MSRP of $375 and is a great bargain considering what the customer gets.  This is probably the lowest price out there for an upper in this chambering.

The DS Arms upper receiver was placed on a LMT Guardian 2000 lower receiver. The AimPoint Comp4S red dot sight with 4x magnifier optics was chosen to test the rifle. Standard GI aluminum magazines were tested as well.

The last rifle tested was the Lewis Machine & Tool LM8 MRP CQB.  This is the only true monolithic rail in the industry as well as with removable barrels bringing a new meaning to modularity for this weapons platform.  The new LM8 lightweight upper receiver was used for this test.  Released at SHOT Show 2012, this streamlined MRP offers removable rail section enabling the user to only put on what rail segments that are needed.  This saves both weight and risk to damage unused rail sections.  In the upper receiver were an LMT standard auto bolt carrier group and an enhanced LMT bolt.  The lower receiver is an LMT selective fire Guardian 2000 lower receiver with a standard H buffer.  The optics mounted was the EOTech XPS3 with the 3x magnifier.

The barrel for the MRP CQB chambered in 300 Blackout is interesting in its configuration.  The barrel is marked for both the 300 Whisper and 300 Blackout.  The 16 inch barrel is chrome plated with a 1/8 inch twist and was test fired with a proof round and then magnetic particle inspected to ensure against any stress fractures.  What is interesting is the short 7 inch gas system as opposed to a standard carbine length or mid-length system.  LMT engineers found that it was more reliable placing the gas port closer to the chamber for reliable feeding with the wide array of bullet weights and velocities.  Nearly 1,000 rounds have been fired through this barrel over the last few months with ammunition manufactured by Remington, Hornady and Barnes.  The LMT rifle had no malfunction issues with any ammunition regardless of it being supersonic or subsonic.  Accuracy maintained an average of 1 inch at 100 yards.  The subsonic tended to group just a hair under in group size, but significantly lower when the optic was zeroed for supersonic ammunition.  Leupold has addressed this issue in cooperation with AAC and released a special 300 Blackout reticle, which is marked for the drop of both super and subsonic ammunition.  This would be a must for any operator, who intends on switching types of ammunition in the field and not having the ability to re-zero.  Unfortunately one was not available at the time of this writing.

Shown below is the natural curvature of 15 rds of 7.62x39mm ammunition, which is caused by the taper of the cartridge case. This is in a nutshell why this cartridge cannot feed reliably in a magazine designed for an AR-15/M16/M4 magazine well. When you compare to the 15 rds of 300 Blackout above, there is far less curvature making the round feed easily and reliably in a straighter magazine. This is the key to the reliable feeding of the 300 Blackout.

There have been many calibers introduced over the past several years for the AR-15 weapons platform that attempted to provide a bump in muzzle energy over the 5.56mm.  Although in some ways excellent cartridges, none have really been widely available until now.  The 300 Blackout, since its SAMMI acceptance, has boomed well beyond calibers such as the 6.8SPC and 6.5 Grendel.  There are more manufacturers making 300 Blackout than any of the other alternative AR-platform, and this was achieved by eliminating the problems that have plagued the 7.62x39mm chambering in the AR-platform and giving the AR-platform user an option of using their weapon system with a cartridge that meets and exceeds the performance of the 0.311 caliber AK round in down-range muzzle energy.  The ability of using super or subsonic ammunition is just the icing on the cake.  This author predicts that the supersonic rounds will by far surpass the use of subsonic, and with that I hope to see some slower rate twist barrels introduced that would be more optimal for the 125 grain projectiles.  The success of this cartridge is certainly a tribute of the genius of J.D. Jones.  His concept has proven its metal over and over.  AAC and Remington were undoubtedly able to give the cartridge the boost to make it recognized around the world and in this industry as the first real competitor to the 5.56mm in this weapons platform.