First shots with the CMMG 5.7 upper on AR pistol lower
The video opens with the CMMG 5.7x28 conversion upper mounted on a Radical Firearms AR pistol lower that was originally set up for .300 Blackout. The host notes that the lower configuration does not matter for this upper and proceeds to chamber a round, commenting on how much he likes the oversized charging handle. After sending a few rounds downrange, he remarks on how enjoyable the setup is to shoot, describing the 5.7x28 as a fast-moving cartridge with very light recoil. He compares it to having a bit more kick than .22 LR but noticeably less blast and push than 5.56/.223, while still offering impressive velocity. The host references the cartridge’s popularity in platforms like the FN PS90, FN Five-seveN, and Ruger-5.7, and mentions that Classic Firearms has SHOT Show coverage of the Ruger pistol for viewers who want more information. He emphasizes that this upper makes the 5.7 chambering a lot of fun and very controllable on an AR-style lower.
Magazines, features, and shooting impressions
The host highlights that the CMMG 5.7 upper ships with three dedicated 40-round magazines. He explains that they resemble standard AR magazines but are specifically designed for the 5.7 cartridge. He praises CMMG for including three mags from the factory, giving the shooter substantial capacity. While shooting, he confirms that the firearm locks back on an empty magazine, demonstrating reliable last-round bolt hold-open. The upper features a short threaded barrel of about five and a half inches, a full-length Picatinny rail along the top, and M-LOK attachment slots around the handguard for accessories. A SIG MSR red dot is mounted as his go-to range optic because it is easy to move between guns and includes a simple tool for mounting and adjustments. The host reiterates that the setup is soft-shooting, fast, and simply a lot of fun on the range.
Radical Firearms lower and overall ergonomics
Attention turns to the Radical Firearms pistol lower itself. The host points out the Mission First Tactical grip, noting its comfortable angle and texture, and says he is impressed with how well the Radical lower pairs with the CMMG 5.7 upper. He encourages viewers to check out Radical Firearms products, mentioning that Classic Firearms carries their pistols and rifles in various calibers. The combination of the Radical lower, the CMMG upper, and the dedicated 5.7 magazines is described as a very slick and ergonomic package. The host again comments on the threaded barrel, the continuous top rail, and the M-LOK handguard, emphasizing that these features make it easy to configure the gun with optics, lights, and other accessories. Overall, he is clearly pleased with how the entire setup handles and performs.
CMMG product lineup and 5.7 upper concept
The host briefly discusses CMMG’s broader lineup, mentioning that the company is known for innovative firearms such as the Mutant series and other 5.7-chambered options, as well as their .22 LR conversion kits. He explains that this particular product is a dedicated 5.7 upper that allows shooters to use their existing AR-15 lowers instead of buying a completely new firearm. This makes it an appealing way to get into the 5.7 cartridge while retaining familiar AR controls and ergonomics. He reiterates that the upper is compact, threaded for muzzle devices or suppressors, and ships as a ready-to-go package with multiple magazines, making it a compelling option for those who want a lightweight, low-recoil, high-capacity configuration.
Switching to Daniel Defense Mk18 with Echo trigger
To close out the shooting portion, the host mentions that he has one more experiment in mind. He brings out his Daniel Defense Mk18, a short-barreled rifle lower that has something special installed: a Fostech Echo trigger. He swaps the CMMG 5.7 upper onto the Mk18 lower and hints that viewers probably expected to see a full magazine emptied using the Echo mode. The segment sets up a demonstration of how the upper runs on a premium SBR lower with a fast-reset trigger system, showing the versatility of the CMMG upper across different AR platforms and hinting at the impressive volume of fire that can be delivered while still operating within the legal definition of one round per mechanical action.
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