What's The Deal With The 300 Blackout? Cartridge Review

Back in 1993, my longtime friend J.D. Jones of SSK Industries called to inform me that he had developed just over a dozen reduced-capacity cartridges designed to be loaded to subsonic velocities. As most experienced shooters know, most of the loud noise heard when a rifle is fired is produced by rapidly expanding propellant gas exiting the muzzle and entering the atmosphere. Attaching a suppressor to the barrel does not eliminate that noise entirely, but it does reduce the noise. It leaves the small sonic boom created by the bullet as it exceeds the speed of sound. Keeping the velocity of a bullet just below 1,100 fps eliminates that bit of noise. The dozen or so subsonic wildcats created by Jones ranged from the 6mm Whisper on the .221 Remington Fireball case to the .510 Whisper on a modified .338 Lapua Magnum case. Of those on the Fireball case, the .300 Whisper proved to be the most promising because it delivered greater energy than its siblings, which were loaded with lighter bullets of smaller diameters. Converting an AR-15 in .223/5.56mm to .300 Whisper required little more than switching barrels. Standard AR magazines worked equally well.

At the time Jones was loading the .300 Whisper with 220-grain and 240-grain match bullets at a muzzle velocity of 1,040 fps, and while they did not expand when impacting soft targets, the increase in diameter made them more deadly than full-metal-jacketed .22-caliber bullets fired from the 5.56mm NATO cartridge. Thus, the .300 Whisper represented an easy way for members of law enforcement and the military to improve the stopping power of the AR-15 rifle. More specifically, the cartridge was intended as a more potent replacement for the 5.56mm in the M4 carbine as well as 9mm submachine guns used by the Navy SEALs and other special operations troops. Due to the rapid drop of its slow-moving bullets, the .300 Whisper was never intended for engaging targets at long distances. During my conversation with J.D., he mentioned that RCBS reloading dies, .221 Fireball cases, and a .300 Whisper upper for my AR-15 were headed my way. Included in the package were several pages of pressure-tested subsonic and supersonic load data that must have taken a lot of time and money to develop. I was not surprised by the then-new cartridge because I had been shooting varmints and big game with guns chambered for a dozen or so of the numerous wildcat cartridges developed by him over the decades. But I really was not too excited by his latest creation because I could think of no reason why I would want to shoot rifle bullets at subsonic velocities. And even when loaded to supersonic speeds with lighter bullets, performance of the .300 Whisper still fell short of the 7.62x39mm Russian I was shooting in an SKS-45 carbine as well as a Ruger Mini-30.

Then one dark and rainy day, J.D. learned that Advanced Armament Corporation had teamed up with Remington (who sponsored the cartridge with SAAMI) and changed the name of his .300 Whisper to .300 AAC Blackout. (Remington went on to purchase Advanced Armament Corporation in 2009.) The two cases are virtually identical, and while chamber throat length for the Blackout is said to be 0.015 inch longer, it can vary, and chamber reamer drawings I have seen indicate just the opposite. Regardless, reloading dies made years ago for the .300 Whisper work as well for the .300 Blackout as those made for it today. SAAMI maximum cartridge length is 2.260 inches, same as for the .223 Rem. Prior to the introduction of a line of Sub-X bullets in 0.308-, 0.357-, 0.452-, and 0.458-inch diameters by Hornady, a jacketed rifle bullet that would expand at subsonic impact velocities did not exist. Due to a soft lead core enclosed by a thin jacket with deep skiving at its hollow nose and the soft Flex-Tip insert, Sub-X bullets are said to expand at impact velocities as low as 900 fps. Their construction meets FBI protocol for terminal ballistic test requirements. The 190-grain version is available for handloading and in Hornady’s Subsonic loading of the .300 Blackout at a velocity of 1,040 fps. Propellant in the round is optimized for carbine-length barrels. Sometime back the company began supplying the ammunition to an unspecified military unit within the Department of Defense for close-quarters battle (CQB) use. I find that the 190-grain Sub-X bullet works equally well for subsonic loading of the .308 Winchester cartridge.

The 2023 Hodgdon Annual Manual has subsonic load data for the .300 Blackout with bullets weighing from 190 to 230 grains. A dozen or so different powders are included. When developing a load for a new rifle, I begin with a recommended powder charge from that source, and if velocity proves to be a bit low, the charge is gradually increased until I reach a velocity around 1,050 fps. Once that point is reached, 10 rounds are slow-fired over chronograph screens to confirm that bullets are receiving enough push to exit the barrel. Verification can also be accomplished by shooting a paper target, pausing to peep through a spotting scope between each shot. Drastically reducing one of Hodgdon’s pressure-tested loads is not a good idea, as doing so can leave a bullet stuck in the barrel. Should my warning be ignored, rest the unloaded rifle muzzle up and pour a bit of Kroil penetrating oil down its bore and against the front of the lodged bullet. After a one-hour soaking, take a brass rod or hardwood dowel of a diameter matching bore diameter as closely as possible, insert it into the barrel from its breech end and against the base of the bullet, and push the bullet from the barrel. Several taps on the rod with a small hammer may be required to get the stuck projectile to move.

While the original intended role of rifle ammunition loaded to subsonic velocity was for use by military and law enforcement personnel against really bad people, today it is occasionally promoted for hunting big game. As a longtime hunter who strongly believes in the ethical treatment of game animals, I adamantly disagree with that practice. When exiting the muzzle of a rifle at 1,050 fps, the 190-grain Sub-X bullet strikes a 100-yard target with no more than 500 foot-pounds of energy. The .30 Carbine, seldom regarded as entirely suitable for use on deer, delivers over 600 ft-lbs at 100 yards. Enough said on that subject. Loading the .300 Blackout to supersonic velocities will increase its effectiveness on game, but I believe it is best suited for shooting at distances that do not greatly exceed 100 yards. At that distance, some supersonic factory ammunition as well as handloads deliver 1,100 ft-lbs of energy, placing the .300 Blackout close on the heels of its closest rival, the 7.62x39mm Russian.

Load data for the .300 Blackout in the 11th edition of the Hornady reloading manual has maximum velocities of 1,650 fps for the 195-grain BTHP Match and 1,500 fps for various bullets weighing 208 grains. Due to lack of expansion, neither of those bullets would be a good choice for bagging a supply of venison. While the 190-grain Sub-X bullet was designed to expand at subsonic velocities, its recommended velocity range is 900 to 2,000 fps, yet data for it in the Hornady manual stops at 1,200 fps. There is a reason for that. With that bullet seated to the recommended overall cartridge length of 2.070 inches, it occupies about 50 percent of the powder cavity of the case, which is quite small to begin with. The 190-grain bullet can be pushed faster, but not by much simply because charges of various powders used by Hornady to reach a velocity of 1,200 fps leave almost no room for adding more. I did manage to squeeze in a couple more grains of Accurate 1680 for velocity gains of 262 fps from the Ruger American and 304 fps from the Ruger Mini-14 test rifles. Being a bit shorter, the 175-grain Sub-X bullet does not occupy as much powder space inside the .300 Blackout case. Due to that, along with its lighter weight, it can be pushed about 300 fps faster than its 190-grain mate, and that should make it a better choice for use on deer and other game of that size.

While the popularity of noise suppressors on rifles continues to grow, and I am a strong supporter, only about 5 percent of recreational shooters in our country own the devices. And since the majority of shooters who have bought, or will buy, a Mini-14 in .300 Blackout will shoot them unsuppressed but are interested in low-recoil subsonic ammunition for personal-defense use, I purposely did not equip the little rifle with a suppressor to see how well it would function. Opinions differ. According to one report, the Mini-14 gobbled up everything short of the shooter’s lunch, while another source gave the little rifle a thumbs down in that respect. The Mini-14 I have refuses to cycle with subsonic ammo. Moving to the positive side, it never misses a lick with supersonic ammo, and like the Ruger American Ranch, feeding from magazine to chamber is totally reliable with ammo loaded with bullets having all sorts of nose profiles, including the Hornady 100-grain Short Jacket and the Speer 130-grain bullet with its flat nose. Respective magazine capacities for the Mini-14 and the Ruger American Ranch Rifle are 20 and 10 rounds.

Having shot only paper with rifles in .300 Blackout, I am no expert on choosing bullets for hunting, but there appear to be several logical options to try. For surprising called-in coyotes and for sneaking up on a wily old groundhog, I doubt if anything would do a better job than Hornady’s innocent-looking (and fairly inexpensive) 100-grain Short Jacket with plenty of soft lead exposed up front. The velocity range recommended by Hornady for that bullet is 1,800 to 3,100 fps. I have no desire to shoot a deer with the .300 Blackout, but if someone twisted my arm hard enough to change my mind, I would have to let a flip of the coin choose between the Speer 130-grain SPFN and the Hornady 135-grain FTX. Both were designed for the .30-30 Winchester cartridge and should work fine from the .300 Blackout out to the far end of 100 long paces. On the other hand, Hornady’s 110-grain CX at 2,400 fps or the 175-grain Sub-X at 1,700 fps might be as good or perhaps even better. Popularity of the little cartridge has not been restricted to the United States. I enjoy hunting Asiatic buffaloes in Australia with several rifles, including a Ruger Model 77 Magnum in .416 Rigby, and during one of my trips there, I met a gunsmith who specialized in rebarreling .223 Rem. Remington Model 7615 slide-action rifles for the .30-221, as he called his own version of the .300 Whisper. Regardless of the name it goes by, I know of no other rifle cartridge that is commonly loaded with bullets that are longer than its case.

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