Lately, the most prolific and talked about 223/5.56mm alternative found in ARs, is the 300 AAC Blackout. The 300 ACC Blackout utilizes a .223 parent case shortened to 1.368″ and necked up to accept .308″ diameter bullets. Available in both supersonic and subsonic factory offerings, the 300 AAC utilizes the same parts as a 223/5.56mm carbine, with the exception of the barrel, making this an easy conversion for a shooter who already owns an AR15.
For this article, we obtained a Advanced Armament Corporation (AAC) 16″ 300 AAC Blackout upper, Redding dies, and bullets from Brownells. Remington Arms, shipped us three different factory cartridges; 125 grain OTM, 125 grain Accutip, and 220 grain OTM.
The Advanced Armament Corporation (AAC) 16″ 300 AAC Blackout upper ships fully assembled and ready to mount. The 16″ 1:7 twist barrel is nitrided and threaded 5/8″x24 to accept AAC’s 51T Blackout flash hider. The upper has M4 feed ramps and houses an M16 style Bolt Carrier group that is chrome lined with a well staked gas key. A Knights Armament URX II free float forearm with integral folding front sight finishes off the upper.
For testing purposes, we mounted our upper receiver assembly on a Bushmaster lower equipped with a BG-16 pistol grip, Magpul CTR stock, and a Wilson Combat TTU-Mil trigger. AAC specifies a regular weight buffer for their 16″ upper, so we brought both an “H” marked buffer and standard weigh buffer to test.
Testing was conducted on a sunny, 76F day with no wind; sun at 1 o’clock position to the shooter. For our initial accuracy testing, we mounted a Leupold LR/T Mark 4 3.5-10x40MM M1 scope in a GG&G QD scope mount. A DEA six dot target was placed at 50 yards (the 100 yard line was unavailable) and a laser boresighter was used to adjust the scope. From a backpack supported prone position, two initial 3-round groups were fired to establish a zero and then 5-round groups were fired for accuracy. After two groups were fired with each cartridge using the “H” buffer, it was then removed and replaced with a standard weight carbine buffer. As expected, POI of both 125 grain loads was the same at 50 yards; with the 220 grain load impacting 2″ to the right, and 3″ beneath the 125 grain offerings.
Velocity information was obtained using our MagnetoSpeed barrel mounted ballistic chronograph. With a magnetic sensor mounted to the end of the barrel and connected to the data unit via a cable; the MagnetoSpeed chronograph is easy to use and provides accurate readings in all light conditions without the complicated set up associated with traditional chronographs using sky screens. We took the time to shoot our Arsenal converted Saiga AK47 for comparison purposes.
Remington 125 grain OTM: heavy buffer 2208 fps, SD 6, regular buffer 2213 fps, SD 15, five shot groupings from .862″-1.469″ @ 50 yards
Remington 125 grain Accutip: heavy buffer 2298 fps, SD 25, regular buffer 2308 fps, SD 19, five shot groupings from .893″-1.092″ @ 50 yards
Remington 220 grain OTM: heavy buffer1072 fps, SD 19, regular buffer 1090 fps, SD 20, five shot groupings from .955″-1.409″ @ 50 yards
Arsenal AK47 (comparison) Brown Bear 123 grain HP: 2326 fps, SD 16
Following the accuracy and velocity data collection, we decided to see how the cartridge would function under field conditions. To do this we selected and shot some of Paul Howe’s, Combat Shooting and Tactics (CSAT) standards at 50 and 7 yards. When discussing the the 300 AAC amongst friends, the question of recoil came up; so, we wanted to see how this played out under multiple shot scenarios.
Removing our Leupold Mark 4, we replaced it with the Brownells exclusive EoTech CQB T-Dot holographic sight. Based on the ESPX2, the CQB T-Dot utilizes a special reticle that provides a 7, 50/200 and 500 yard aiming point. The sight comes equipped with a built in QD mount. Using the 7 yard T-dot to zero, we were able to hit a 1/2″ dot at 7 yards in 5 rounds. Moving to 50 yards we were able to confirm our zero using the center 1 MOA dot.
Howe’s CSAT standards are shot from the low ready position with the muzzle below the belt, rifle on safe and shooter looking downrange at the target. The target, typically a CSAT target (modified IPSC target with a bold black line around A and B boxes) can also be an IPSC cardboard target, as it was in this case. All hits must be in the “A” zone and within the allocated time for the standard.
CSAT standards were fired with Remington 125 grain OTM loads
- Standard 8, 5 kneeling at 50 yards: Times ranged from 14.25-17.10 seconds
- Standard 1, 1 shot in 1 second at 7 yards: .92, .75, .65, .66, .70 and .61 seconds (average time of .72 seconds)
- Standard 2, 2 shots in 1.5 seconds at 7 yards: .92, 1.01, .89, .96, .90, and .97 seconds (average time of .94 seconds)
- Standard 2/1, 2 to the center box, one to the head box at 7 yards in 1.7 seconds: 1.48, 1.73, 1.35, 1.47, and 1.40 seconds (average time of 1.49 seconds)
- Standard 3, 5 to the center box, one to the head box at 7 yards in 3.0 seconds: 2.14 seconds (note: we were running low on ammunition at this point of the test, the time was well below established par)
During testing, we noticed that the 220 grain OTM subsonic load did not seem to recoil as heavily at the 125 grain loads. To see how this would translate to rapid fire, we shot standard 2 and 2/1 twice each with the load. Note that the times achieved were similar to those with the lighter cartridge.
- Standard 2, 2 shots in 1.5 seconds at 7 yards: 1.00 and .97 seconds
- Standard 2/1, 2 to the center box, one to the head box at 7 yards in 1.7 seconds: 1.55 and 1.36 seconds
Shooting Howe’s standards, we did not experience any problems with the upper receiver’s functioning. While the 220 grain OTM did not lock back the bolt with either buffer, the other rounds did. While the recoil impulse of the 300 AAC Blackout is heavier then the .223/5.56mm, it is still relatively light and manageable. As shown with the CSAT standards, a skilled shooter can easily run the rifle within prescribed par times. Keep in mind, this rifle is equipped with a 5.5 pound trigger and each round was fired with its own sight picture- pretty impressive.
Accuracy with all cartridges was in the 2-3 MOA range, which is acceptable for this kinds of rifle configuration.
While it is well documented that the round is especially well suited for suppressors (which we did not test) it also offers AR15 owners another option for a heavier round by simply replacing the barrel. As we discussed in our 30 AR and 7.62x40WT reviews, there is merit to hunting with a rifle you shoot often. For many, this means an AR15 platform.
For defensive use, the 300 AAC Blackout has similar external ballistics to the 7.62×39 as shown above, without having to rely on the .22 caliber bullet of a 5.56mm.
While the 30AR offers more power, this comes at the price of a proprietary bolt, magazine and cartridge. Both the 300 ACC Blackout and 7.62x40WT offer the carbine shooter 30 caliber bullets with a simple barrel switch. Both use the 5.56x45mm case, but 300 AAC Blackout is available in far more factory loadings . We did find the 7.62x40WT more accurate (most likely due to the slower twist); however, the 300 AAC Blackout has a larger following, with limited use by military and law enforcement agencies.
Not strictly limited to suppressed usage, the 300 AAC Blackout offers AR15 shooters a solid hunting or defensive cartridge with a simple barrel change. The 300 AAC Blackout is here to stay.
For 300 AAC Blackout uppers, barrels, ammunition, and reloading supplies, be sure to check out Brownells. For more information on Remington ammunition, please check out Remington’s website.