CMMG Resolute 100 MKG AR-15 .45 ACP 16″ Rifle

Description

Picture this: you want the familiar, modular control of an AR-15 platform but chambered in a heavy-hitting, proven pistol caliber. You also want magazine compatibility with one of the most common handguns on the planet to keep costs down. That’s the exact scenario the CMMG Resolute 100 MKG AR-15 .45 ACP, 16″ Barrel, M-LOK, Glock Mags, Black, 13rd is built for. It’s a direct-blowback AR-pattern pistol caliber carbine (PCC) designed from the ground up to use readily available Glock-pattern .45 ACP magazines, offering a potent and practical package for range use, home defense, or competition on a budget.

Here’s the thing—building a dedicated .45 ACP AR can get expensive fast, often requiring specialized lowers and proprietary parts. CMMG’s Resolute 100 MKG sidesteps that by integrating a Glock magazine well directly into its forged lower receiver. This means you get a rifle that’s drop-in ready with the magazines you might already own, saving you the hassle and cost of hunting down rare, expensive dedicated mags. At $1409.99, it positions itself as a complete, no-fuss solution compared to the combined cost of a separate lower, upper, bolt carrier group, and buffer system you’d need to piece together yourself.

Key Features & Practical Value

The 16-inch barrel is a smart choice. It gives you a full rifle-length sight picture and maximizes the velocity potential of the .45 ACP round without venturing into the tax-stamped NFA territory of a short-barreled rifle. The barrel features a 1:16 twist rate, which is optimized for stabilizing the heavier .45 caliber projectiles. The entire system uses a straightforward direct blowback operation, which is inherently reliable with stout pistol rounds and keeps the overall mechanical complexity—and potential repair costs—low.

Up front, you get a 13-inch M-LOK handguard. This is where the value proposition shines. M-LOK is the modern, lightweight standard for attaching lights, grips, and other accessories without the bulk and weight of older rail systems. It’s a no-fee platform, so you can shop for budget-friendly M-LOK parts from dozens of manufacturers without being locked into one expensive ecosystem. The handguard provides ample real estate for a proper support-hand grip, which is crucial for managing the distinct push of the .45 ACP’s recoil impulse in a rifle platform.

The heart of the system is its magazine compatibility. The lower receiver is machined specifically for Glock 21 .45 ACP magazines. This is a huge benefit for budget-conscious shooters. Glock mags are famously durable, widely available, and relatively inexpensive. You aren’t tied to a single-source, high-cost proprietary magazine, which dramatically lowers your long-term cost of ownership and increases logistical simplicity. The rifle comes with one 13-round magazine, giving you a starting point right out of the box.

Specifications

Spec	Detail
Caliber	.45 ACP
Barrel Length	16 inches
Handguard	13″ M-LOK
Magazine Compatibility	Glock 21 Pattern .45 ACP Mags
Included Magazine	13-round
Operating System	Direct Blowback

Pros, Cons, and Who It’s For

Pros: The major advantage is cost-effective magazine commonality. Using Glock mags is a brilliant move for practicality. The 16-inch barrel keeps it a standard title I firearm, avoiding extra paperwork and taxes. The M-LOK system offers modern accessory mounting without added weight. Finally, it’s a complete rifle from a reputable manufacturer—you don’t need to be an AR building expert to get a reliable .45 PCC.

Cons: Direct blowback operation in .45 ACP can feel a bit more sluggish and produce more perceived recoil than a delayed-blowback system, though those systems cost significantly more. The 13-round magazine capacity, while standard for many .45 Glock mags, is lower than what’s available in 9mm PCCs. Some might find the overall weight, a function of its robust construction, to be on the heavier side for a pistol-caliber carbine.

So who is this rifle for? It’s ideal for the shooter who already owns a Glock 21 and wants a carbine companion that shares magazines. It’s a solid option for a home defense role where .45 ACP’s stopping power is desired in a more stable, accurate platform. Competition shooters in PCC divisions looking for a .45 caliber option will find a ready-built contender here. It’s also just a plain fun and affordable-to-feed range toy that offers something different from a standard 5.56mm AR.

Frequently Asked Questions

Q: Will this rifle work with my Glock 21 magazines?

A: Yes, that’s the primary design feature. The CMMG Resolute 100 MKG lower receiver is built specifically to accept standard Glock 21 pattern .45 ACP magazines. It should work reliably with factory Glock mags and most reputable aftermarket versions.

Q: Can I use my existing AR-15 parts and accessories on this rifle?

A: Mostly yes. The lower receiver accepts most mil-spec AR-15 trigger groups, pistol grips, and stocks. The upper uses a standard AR-15 charging handle. The M-LOK handguard is compatible with a vast array of affordable accessories. The bolt carrier group and buffer system are specific to the .45 ACP blowback operation and are not interchangeable with standard 5.56mm AR parts.

Q: Is this considered a pistol or a rifle?

A: With its 16-inch barrel and included stock, this is configured and sold as a rifle. It is a title I firearm, meaning no special NFA paperwork or tax stamp is required for purchase, just a standard FFL transfer required for firearm purchases. It is available at firearms-missouri.com for Missouri residents and nationwide to compliant states.

If the idea of a potent, simple, and magazine-savvy .45 caliber carbine fits your needs, the CMMG Resolute 100 MKG presents a compelling, ready-to-run package. See more details on our product page.