Before we start the side-by-side contrast and comparison between rifle ballistics’ 300 Blackout and 5.56mm NATO, let’s first dive into each of its humble beginnings.

AAC’s take on the .30-cal

Despite being a new caliber, the .300 Blackout has quickly risen to prominence in the last 20 years. It’s been popularly used in Special Operations and other specialized military units due to its ability to suppress the round well with impressive ballistics. Hunters started using these, too, boosting their ability to sneak around their prey.

Advanced Armament Company (ACC) designed the .300 Blackout (300 BLK) in the late 2000s to meet the growing demand for ballistics that can offer less sound noise level. At the same time have more capable firepower and compatibility with the rifles such as M4s and AR-15s.

Its conception initially aimed to achieve similar ballistics to the 7.62x39mm, but with enhanced “stopping power” and can perform in a subsonic velocity using a short-barreled rifle.

“A military customer wanted a way to be able to shoot .30-caliber bullets from an M4 platform while using normal bolts and magazines, and without losing the full 30-round capacity of [the] standard magazine,” said Robert Silvers, director of research and development for AAC.

“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).”

At the start of a new decade, the 2010s, the production for the 300 Blackout commenced. Aside from civilian consumers, the 300 BLK has been inducted into military service in the armed forces of the Netherlands, the United Kingdom, and recently in the United States, particularly in the special operations command. In addition, the US forces selected the .300 Blackout as one of the ballistics for its self-defense weapon, the SIG Sauer MCX Rattler, allowing the firearm to be silently powerful while remaining compact.

300 BLK Technical Specs

• Parent case: .221 Fireball/.223 Remington
• Case type: Rimless, bottleneck
• Bullet diameter: 0.308 in (7.8 mm)
• Neck diameter: 0.334 in (8.5 mm)
• Base diameter : 0.376 in (9.6 mm)
• Rim diameter: 0.378 in (9.6 mm)
• Case length: 1.368 in (34.7 mm)
• Overall length: 2.26 in (57 mm)
• Rifling twist: 1-8″ (203 mm)
• Primer Type: Small rifle
• Maximum pressure (SAAMI): 55,000
• Maximum pressure (CIP): 56,565
• Maximum CUP: 52,000 CUP

5.56mm Time-Tested

Meanwhile, 5.56mm has been around since the 1980s, when it was designed by FN Herstal a decade earlier. It was also derived from the .233 Remington, was widely used by law enforcement, and was generally accepted by gun enthusiasts and athletes. Its wide range of availability and low cost earned it a place among home defense rifles.

While it is undoubtedly among the favorites, 5.56mm has had its fair share of criticism throughout the years, primarily pointing to its alleged poor performance on stopping power, lethality, and range. Others would highlight its poor barrier penetration and accuracy. But these issues depend on the barrel length the 5.56mm is being used. Countries using the 5.56 in military service include Australia, Belgium, Germany, Switzerland, South Africa, the UK, and the US, to name a few.

5.56mm NATO Technical Specs

• Parent case: .223 Remington (M193)
• Case type: Rimless tapered, bottleneck
• Bullet diameter: 5.70 mm (0.224 in)
• Land diameter: 5.56 mm (0.219 in)
• Neck diameter: 6.43 mm (0.253 in)
• Shoulder diameter: 9.00 mm (0.354 in)
• Base diameter: 58 mm (0.377 in)
• Rim diameter: 9.60 mm (0.378 in)
• Rim thickness: 1.14 mm (0.045 in)
• Case length: 44.70 mm (1.760 in)
• Overall length: 57.40 mm (2.260 in)
• Case capacity: 1.85 cm3 (28.5 gr H2O)
• Rifling twist: 178 mm (1 in 7 in) or 229 mm (1 in 9 in)
• Primer Type: Small rifle
• Maximum pressure (EPVAT): 430.00 MPa (62,366 psi)
• Maximum pressure (SCATP 5.56): 380.00 MPa (55,114 psi)

Side-by-side Specs Comparison

To put this side-by-side comparison into context, we’ll consider their performance in terms of technical specifications, recoil, power, range, and, of course, availability and cost.

Based on the specs sheet provided above, we can conclude that the .300 Blackout measures slightly higher than the 5.56mm in bullet, neck, and base diameter. However, the 5.56mm is a little longer in case length. When we compare the two shells, the overall length is basically the same at 57mm.

The 5.56mm typically weighs 55 gr, 62 gr, and 63 gr, which is noticeably lighter.300 BLK typically weighs 78 gr, 110 gr, and 125 gr. As a result, the 300 BLK’s perceived recoil sound has been identified as more robust than the standard 5.56mm bullet.

Now let’s talk about the bullet’s power and range. Because it is lighter, the 5.56mm has proven to have a range of 500 yards at high velocity after extensive training. Nevertheless, the 300 Blackout stands out when shot on a short barrel gun. In a shot test with a 9-in barrel, the 300 Blackout (125 gr) reached approximately 993 ft-lbs at 100 yards, a significant difference from the 5.56mm (55 gr), which only went 191 ft-lbs at the same distance.

Finally, if we’re talking about availability and cost, the 5.56mm has the upper hand. It is the older of the two bullets and has been widely used and manufactured throughout the country. Moreover, because 5.56mm is less expensive than .300 Blackout, almost every gun owner with a rifle has boxes of it.

For more insight into the firepower performance of the .300 Blackout and 5.56mm, check out the videos below.

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Choosing a round, however, is still a matter of personal preference and application. Once you’ve decided what it’ll be used for—whether hunting wild animals, at the practice range, or simply for protection—you’ll know what works best for you, as both have significant advantages.