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SHOP NOWThis video examines how different calibers perform in the AR-15 platform. It focuses on recoil, effective range, and practical roles for each cartridge.
The discussion opens at Take Aim Training and Range with an overview of AR-15 calibers and how the platform has expanded beyond its original 5.56 NATO and .223 Remington chambering. The focus stays on common rifle calibers, avoiding larger bores like .458 SOCOM and .50 Beowulf, and caps the comparison around 7.62 or .30 caliber on the high end. The baseline example is a Knights Armament SR-15 set up with a Vortex Gen 3 1-10 optic and a B5 Systems stock, running 5.56 NATO M855 green tip in a Magpul magazine. The SR-15 is presented as a high-end AR, and 5.56 is framed as the standard U.S. military cartridge that replaced 7.62 NATO in the M14 due to its lighter weight and adequate terminal performance.
The 5.56 NATO cartridge is described as light recoiling and fast, running around 3,000 feet per second from a 20-inch barrel and roughly 2,800–2,900 feet per second from a 16-inch barrel like the SR-15 shown. On steel targets it feels controllable and enjoyable to shoot, reinforcing why it remains widely used. The video notes that 5.56 and .223 Remington are effective and well-understood, with separate content already covering their performance differences. After demonstrating the SR-15 on target and emptying the magazine, the segment closes by acknowledging 5.56 as a solid, familiar standard before moving on to less commonly discussed AR-15 calibers.
The next rifle introduces 6.5 Grendel, contrasted visually with 7.62x39 since both feed from similar magazines, which can create confusion similar to mixing up 5.56 and 300 Blackout magazines. 6.5 Grendel, developed in the early 2000s by the founder of Alexander Arms, is positioned as a middle ground between 7.62 NATO and 5.56 NATO. The cartridge uses a slimmer projectile backed by more powder, with an example 100-grain bullet compared to the 62-grain M855 in 5.56. Muzzle velocity is stated around 2,700–2,800 feet per second. The rifle used is a Fostech (Fostte) Lightning with a 20-round magazine and 30-round DuraMag, setting up a live-fire demonstration of how 6.5 Grendel behaves in the AR platform.
On the range, 6.5 Grendel shows noticeably more recoil than 5.56, though still manageable, especially considering the rifle weighs only about six to seven pounds. The Fostech Lightning is described as comfortable and visually appealing, and the 6.5 Grendel round stands out as an interesting option. The video notes that Serbia, home of Zastava Arms, is reportedly considering 6.5mm Grendel as a primary cartridge for its new M17 rifle, indicating potential military adoption. Ballistically, 6.5 Grendel is presented as offering better downrange performance than 5.56 and, based on cited research, superior terminal ballistics and penetration at 1,000 meters compared to 7.62 NATO. It is suggested as a caliber for shooters wanting to stretch the AR-15’s effective range.
The focus shifts to 7.62x39 in the AR platform using a Maxim Defense PDX 7.62x39 pistol, which is also identified as a giveaway firearm. The host addresses the question of why someone would choose 7.62x39 in an AR when the platform was not originally designed for it. The answer centers on extracting the familiar 7.62x39 performance from the ergonomics and modularity of the AR. The segment acknowledges that some home-built 7.62x39 ARs suffer from reliability and feeding issues, often tied to parts quality or build quality. Viewers are advised to use good components and proper assembly practices when building ARs in this caliber. The PDX, with its compact configuration, is then fired to demonstrate how 7.62x39 behaves in a short-barreled AR pistol.
Firing the Maxim Defense PDX with its approximately 5.5-inch barrel and Hate Brake muzzle device produces a pronounced report and blast. The video notes that 7.62x39 is the world’s most popular caliber, with massive production since the SKS and AK-47 era. It is characterized as very effective inside roughly 300 yards, with the capability to reach farther. The common belief that 7.62x39 is inherently inaccurate is challenged, with the point that ammunition quality matters just as much as it does with inexpensive .223 or 5.56 loads. With decent 7.62x39 ammunition, engaging targets at 500 yards is presented as realistic. The cartridge is portrayed as accurate enough for practical use and particularly enjoyable from AR rifles or pistols like the PDX.
The final caliber covered is 300 Blackout, described as a favorite for close-quarters roles. It is introduced as a cartridge developed specifically for short-range use with suppressors. The featured setup is a Nemo Battle Light pistol equipped with an SBA3 brace and a Yankee Hill titanium .30-caliber suppressor. Although the ammunition used in the demonstration is supersonic rather than subsonic, the suppressed shots clearly sound quieter compared to the unsuppressed 5.56, 6.5 Grendel, and 7.62x39 fired earlier. The segment briefly raises the topic of the terms “silencer” versus “suppressor” as a potential subject for a separate discussion. The emphasis here is on how 300 Blackout pairs naturally with suppression in compact AR configurations.
The discussion closes by outlining where 300 Blackout excels, particularly in contexts like hog hunting in Texas and other close-range scenarios. The .30-caliber projectile can be kept relatively quiet when suppressed, which is useful for nocturnal animals and low-visibility conditions. When combined with night optics or other low-light equipment, a flash suppressor and good flash mitigation become important to preserve the shooter’s vision and concealment. 300 Blackout is presented as well-suited to this role, offering a quiet, flash-controlled option in a compact AR platform. The video notes that beyond its practical advantages, shooting 300 Blackout in this configuration is simply enjoyable, before briefly transitioning toward the topic of firearm giveaways.
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