The 7.62x39 mm cartridge was born in Russia and, carried by the AK-47s and SKSs it runs in, quickly spread across Communist bloc countries. The .300 Blackout, on the other hand, is American born and has the kind of enviable up-close and subsonic performance that quickly gained traction with stateside firearm enthusiasts. One’s relatively new, the other World War II vintage, and both are solid performers in modern sporting rifles.
When it comes to choosing between a 7.62x39 vs. .300 Blackout chambering in your AR-15 upper, there are some differences to weigh. One has a slight advantage downrange, while the other has Swiss Army Knife-rivaling versatility.
History
7.62x39 mm
The Red Army finally won the long and hard-fought Battle of Stalingrad against Nazi Germany in early 1943 and those bloody small-arms engagements and strained supply lines were fresh on the minds of a Soviet technical committee convened a few months later. Their mission was to come up with a cartridge that performed reliably in light machine guns, select-fire rifles and carbines. The group, which included Communist Russia’s most accomplished firearm experts, selected the 7.62x39 mm. It was officially adopted by the Kremlin that year, receiving the military label as the M43.
The 900-day siege of Leningrad was still underway, however, and the outcome of World War II was still far from certain. The cartridge and firearms chambering it were a priority, although production didn’t begin until 1944. It wasn’t until 1945 when the Simonov SKS that first digested the cartridge appeared.
It was the AK-47, however, that made the 7.62x39 mm an indelible part of firearm history. Work on that gun didn’t begin until 1945, with its completion and approval only two years later. The Russian military fielded it in 1949 and its unfailing reliability and performance quickly spread it and its complementary ammo across the globe.
The Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) has approved and standardized the 7.62x39 mm for commercial use. Companies have adhered to the organization’s specifications for nearly a century, ensuring cartridge and chamber dimensions and pressures remain within prescribed dimensions and pressure tolerances. Maximum average pressure for the cartridge is 45,000 psi.
.300 Blackout
In 2009 Advanced Armament Corporation (AAC) began development of a .30-caliber cartridge capable of running in an M4. The work was originally an effort to meet a U.S. military search for improved stopping power from the arms issued to our troops, without needing to replace the lower receivers or standard 5.56 NATO magazines in circulation.
J.D. Jones had already done a lot of the groundbreaking work. His .300 Whisper, which uses heavy bullets launched at subsonic speeds, gained a solid reputation for performance among sportsmen who wanted to quiet their modern sporting rifle’s report, whether at the range or on opening day.
On Jan. 17, 2011, SAAMI approved and standardized the .300 Blackout cartridge with a maximum average pressure of 55,000 psi. The .300 Whisper, however, hasn’t achieved the same status with the organization, although it’s not for lack of performance or reliability.
7.62x39mm Loads
One of the big advantages of 7.62x39 is the abundance of imported, usually inexpensive steel-cased ammunition wearing full-metal-jacket bullets. If you’re a high-volume shooter, going with one of Bear Creek Arsenal’s 7.62x39 uppers is an option that will extend your firing line sessions without breaking a budget. In addition, domestic companies make easy-on-the-pocketbook FMJ options.
Stateside manufacturers also offer loads better suited for hunting or home defense. Winchester, for example, offers a PDX1 Defender load with a 120-grain protected hollowpoint bullet that harnesses the company’s Split Core technology. The copper-jacketed projectile is specifically designed for unfailing feeding in semi-automatics.
If you’re looking forward to opening day the company also makes a 123-grain Deer Season XP load. Its Extreme Point bullet one-shot terminal performance tailored to fill tags. The number of manufacturers expanding their options in this cartridge has continued to expand and shows no signs of slowing.
Downrange Comparison
When it comes to performance downrange, the 7.62x39 Vs. .300 Blackout differences show, despite the fact both cartridges are .30-caliber—.308-inch. That diameter is one of the sweet spots for long-distance connections according to some. The 7.62x39 mm SAAMI specs allow it to go slightly wider, which may explain a slight gap in performance.
The Winchester Deer Season XP cartridge in 7.62x39 mm, for example, sends its 123-grain bullet out of the barrel at 2,380 fps. It generates 1,547 foot pounds of energy at the muzzle.
Zeroed at 100 yards, it drops roughly 6.5 inches at 200. At that distance it hits with 947 foot-pounds of energy, more than enough to fill a tag.
Winchester’s .300 Blackout USA White Box cartridges wear a 125-grain open-tip bullet and provide the best bullet weight and trajectory comparison in the company’s lineup (sticking with one manufacturer to minimize chances that different barrel lengths were tested). Muzzle velocity is 2,185 fps, nearly 200 less than the 7.62x39 mm. At the barrel it’s generating 1,325 foot pounds of energy, a drop of more than 200.
At 200 yards its moving 1,632 fps, carrying 732 pounds and has dropped 7 inches, again taking a backseat to the 7.62x39 mm. Before deciding the older cartridge is your best choice, though, there are several other considerations.
.300 Blackout Loads
The diversity of 300 Blackout cartridges and loads is downright staggering. It’s this fact that makes it more versatile than the 7.62x39, despite the exterior ballistics difference. Bear in mind, though, with the increasing number of enthusiasts only now discovering the latter’s performance, ammunition manufacturers will likely soon begin offering more options in their lineups.
The .300 Blackout may be the ultimate choice if you own a suppressor or are considering purchasing one. The reduced report is music to the ears, neighbor friendly and when hunting, no sonic boom further minimizes the chances of big game triangulating your position should your first shot be off the mark.
Winchester offers a 200-grain load that doesn’t break the speed of sound. Federal offers the same advantage in a 220-grain version and there are many others from which to choose. Finding bullets that heavy and launched that in 7.62x39 mm loads is tough.
Projectile designs are also more diverse in .300 Blackout. Everything from FMJs to hunting and home-defense options are available commercially. Whether it’s a day at the range on the schedule or opening day, odds are good you can find exactly what you need. Unlike the 7.62x39 mm, don’t expect to run across bulk packs at bargain-basement prices.
Compatibility
Complete AR-15s chambered in either cartridge are available today. Bear Creek Arsenal offers a .300 Blackout version with a 16-inch barrel, a pistol with 8.5-inch barrel and others. If you prefer 7.62x39 mm the lineup includes a carbine, pistol and more. [Shop 300 Blackout uppers and 7.62x39 uppers here from Bear Creek Arsenal!]
If you already own a modern sporting rifle in 5.56 NATO, however, a more budget-friendly option is to simply select an upper. Installation is fast, easy and user friendly. In fact, you perform most of the process every time you field strip and clean your AR-15.
Because the lower receiver is the serialized component on a modern sporting rifle, adding an upper to your gun safe doesn’t require FFL intervention or paperwork. The versatility of another chambering while maintaining those familiar fire controls and trigger pull is a big advantage.
Magazines
By design, standard 5.56 NATO/.223 Rem. magazines will run .300 Blackout ammunition in an AR-15. That means you can still use all those 30-round standard capacity versions you have stockpiled without any additional purchase.
The geometry of the 7.62x39 cartridge is slightly different, however. Some AR-15 magazines will work with the cartridge, others stovepipe after a few cartridges. A few firing-line sessions will tell the tale. An aftermarket purchase may be the best solution and we offer 10-round stainless steel magazines that have been tested extensively and work well.
Bear in mind, however, with that added versatility comes added responsibility. You don’t want to inadvertently toss a magazine loaded with .300 Blackout or 7.62x39 mm ammo into a 5.56 NATO upper. Some claim the cartridges won’t chamber but, as they say, an ounce of prevention…
Unload the magazines after each range session for safety sake. Designate different magazines for each cartridge and clearly mark them with a paint pen. And double check headstamps before loading or starting a match.
Recoil
Perceived recoil reduces as the bolt carrier group taps energy to cycle in a gas-operated semi-automatic like the AR-15. Both cartridges have very little recoil, although it is more than generated by a 5.56 NATO-chambered modern sporting rifle.
Most consider the 7.62x39 mm very friendly to new shooters, regardless of load. That makes follow-up shots fast and trips to the range a pleasure, regardless of round count. The .300 Blackout is about the same, although its cartridge diversity and subsconic ammo expand the options considerably.
Which One is The Best?
When it comes to choosing between 7.62x39 mm Vs. .300 Blackout for your AR-15, you can’t go wrong. Both are solid performers and, depending on your passion for the shooting sports, deliver.
If high-volume plinking is your pleasure and budget is a concern, 7.62x39 is likely the optimal choice. Bulk, steel-cased ammo at bargain-basement prices isn’t hard to find, although that may change as supply is already straining due to the recently announced Russian ammo ban. Thankfully, there are plenty of other offshore sources ready to fill that vacuum. The measure could also be lifted in 12 months.
If hunting is your passion or home defense the priority, there’s no denying the .300 Blackout is currently a better option. The advantage here is the diversity of bullets that factory-fresh cartridges wear, many delivering controlled expansion on target.
Then there are the commercially available subsonic loads. A former coworker is the only deer hunter allowed on an alpaca farm, one in which the overpopulation of wildlife is a growing concern. Unfortunately, the report of some firearms seems to negatively impact their livestock, so the owners extend the exclusive invitation annually with the stipulation that he uses his suppressed .300 Blackout and subsonic loads for the management hunt.
As more and more enthusiasts discover the performance of the 7.62x39 mm the demand will force manufacturers to increase the variety of loads wearing higher-performance bullets. That makes an AR chambered for the cartridge a solid investment, one that will provide any enthusiast with long-term gains, regardless of pursuit. Looking shorter term, however, when next year’s hunting season or guard duty at the homestead this week is the priority, the .300 Blackout and its cartridges are my personal pick.
[Leave a comment below with your thoughts about 300 Blackout vs 7.62x39 and check out our other articles like our guides to 9mm Carbines and 6.5 Grendel.]
