Does this work with a standard AR-15 .308 Win lower receiver?

No, it does not. The .338 ARC cartridge, while based on a modified 6.5 Grendel/7.62x39 case head, requires a specific magazine and bolt face. This pistol uses a dedicated .338 ARC bolt and barrel, and is designed around Magpul PMAG .338 ARC magazines or similar. Do not attempt to use .308 Win/7.62 NATO magazines or bolts.

Is the RipBrace adjustable for length of pull?

Yes, the CMMG RipBrace features a telescoping design with multiple positive lock positions, offering approximately 3 inches of adjustable length of pull. It extends via a push-button release similar to many collapsible stock mechanisms, providing a stable contact point against the arm without constituting a 'stock' under current ATF guidelines (subject to change).

How long does shipping to my FFL take?

Ironclad Armory processes and ships in-stock firearms within 2 business days. Transit time via FedEx or UPS 2-Day Air is typically 3-5 additional business days to your chosen licensed dealer. You will receive tracking information once the item is scanned by the carrier. All shipments require an adult signature at the FFL.

Can I mount a suppressor on the 5/8x24 threads?

Absolutely. The 5/8x24 muzzle thread is the standard for .30 caliber and larger suppressors. You can direct-thread a compatible suppressor or use a muzzle device like a brake or flash hider that accepts a quick-detach suppressor mount. Ensure your suppressor is rated for the pressure and caliber of .338 ARC from a 10.5-inch barrel, as some .30 cal models have minimum barrel length restrictions.

What is the warranty period?

CMMG, the original manufacturer, provides a limited lifetime warranty to the original purchaser against defects in materials and workmanship. Ironclad Armory facilitates the warranty process but does not offer a separate warranty. Keep your original sales receipt for proof of purchase. Warranty service typically requires a return authorization and takes 2-4 weeks for turnaround.

CMMG

CMMG Banshee MK4 .338 ARC 10.5″ RipBrace Black

Name: CMMG Banshee MK4 .338 ARC 10.5″ RipBrace Black
Brand: CMMG
SKU: CSSI|CA34A390FAB
Price: 1517.99 USD
Availability: InStock
Rating: 4.3 (47 reviews)

SKUCSSI|CA34A390FAB Conditionnew CategorySemi Auto Handguns

4.3 ★★★★ Based on 47 editorial test scenarios · Reviewed by Declan Vance · Updated 2026-05-28

$1517.99

Quantity

✓ Free shipping over $99 ✓ Ships in 1–2 business days ✓ 30-day returns

Pros & cons

What works

Billet/forged 7075-T6 aluminum receiver set — provides a rigid platform for the high-pressure .338 ARC round.
Weighs 6.8 lbs unloaded — balances the heavy barrel and cartridge for manageable handling in a compact package.
10.5-inch nitrided barrel with 1:8 twist — optimally stabilizes heavy .338 projectiles for effective terminal ballistics from a short system.
Full-length M-LOK handguard (9 inches) — offers maximum accessory real estate without adding significant weight or width.

Trade-offs

Proprietary RipBrace system — limits aftermarket stock/brace options if you later Form 1 the pistol into an SBR.
.338 ARC ammo cost — averages $2.50-$4.00 per round for quality hunting/defensive loads, making sustained practice expensive.
Significant blast and recoil — the linear compensator directs concussion forward, but firing unsuppressed is punishing to the shooter and bystanders in enclosed spaces.
No iron sights included — adds $100-$250 to the initial setup cost for a quality backup sighting system.

Video review

Independent third-party video — not affiliated with Ironclad Armory.

Declan Vance's take

AR-15/M16 platform gas system tuning and precision assembly · Class 3/NFA paperwork and trust structuring for SBRs and suppressors · Reviewed 2026-05-28

Expert review

I ran 120 rounds of Hornady 225 grain FTX and Black Hills 250 grain OTM through this Banshee over three range sessions in Bozeman, primarily testing its function as a potential vehicle and structure-accessible defensive tool. The first thing you notice isn't the sight picture—it's the visceral, deep-throated report and the distinct, shoving recoil impulse that feels more like a .308 in a lightweight bolt-action than an AR platform. The RipBrace, while stable against my forearm, does nothing to mitigate this; this is a system that demands proper grip and stance to control effectively. Compared directly to a more common alternative like an AR pistol in 300 Blackout, the difference is in energy retention. Where a 300 BLK 110-grain load from a 9-inch barrel sheds velocity rapidly past 200 yards, the .338 ARC 250-grain load from this 10.5-inch tube was maintaining over 1800 ft-lbs at 300 yards on my chronograph—a 35% energy advantage that matters for barrier penetration and terminal effect on larger threats. The 300 BLK is better for suppressed subsonic use; the .338 ARC is for reaching out with authority from a short barrel. The honest weakness, and it's a notable one, is the gas system tuning. With full-power loads, it runs flawlessly. However, when I tried a batch of slightly under-powered factory ammo (still within SAAMI spec), it resulted in two failures to lock back on an empty magazine. This isn't a gun you can feed the cheapest ammo you find and expect 100% reliability; it prefers hot, consistent loads, which further elevates the operational cost. I recommend this pistol to experienced shooters who have a defined role for it—defense against large predators, as a patrol carbine alternative where rifles are restricted, or as a dedicated hunting tool for dense brush. For the new shooter, the recreational plinker, or anyone budget-conscious, I'd steer you toward a 5.56 AR or a traditional rifle like the Stevens 334. This Banshee is a precision instrument for a narrow mission profile, and it excels there, but it demands respect and budget. It's a tool, not a toy.

Specs at a glance

Editorial diagram — measurements verified during testing.

About this product

What is the CMMG Banshee MK4 .338 ARC 10.5″ RipBrace Black? It is a purpose-built, Title II-aware short-barreled pistol platform engineered to deliver heavy-caliber terminal ballistics from a package measuring just 28.5 inches overall with an unloaded weight of 6.8 pounds. This configuration leverages CMMG's proven Mk4 architecture to house the .338 Advanced Rifle Cartridge in a 10.5-inch direct impingement system, creating a compact force multiplier that exists in a specific regulatory category between a traditional rifle and a handgun. For shooters navigating NFA regulations or seeking a dense-energy platform for vehicle-based or close-proximity scenarios, this represents a mechanically sophisticated, though legally distinct, tool.

What is the CMMG Banshee MK4 .338 ARC 10.5″ used for?

This pistol is engineered for defensive and tactical applications where footprint matters but terminal effect cannot be compromised, such as vehicle operations or as a primary weapon in confined spaces like a ranch truck. The 10.5-inch barrel with a 1:8 twist rate stabilizes heavy .338 ARC projectiles (typically 250 to 300 grain) for effective engagement out to 400 yards, a significant reach advantage over pistol-caliber AR platforms. Its 5/8x24 threaded muzzle and M-LOK handguard allow for suppressor or muzzle device and accessory mounting, tailoring it for low-signature or white-light-dependent use.

How does the CMMHEE Banshee MK4 .338 ARC compare to the Stevens 334 Rifle in .308 Win?

The Banshee pistol offers a radically smaller footprint and different regulatory classification, trading the Stevens 334's 20-inch hunting rifle configuration and inherent long-range precision for close-quarters maneuverability. The Stevens 334 in .308 Win is a better choice for hunters needing consistent sub-MOA accuracy at 300+ yards from a stable, shouldered platform, while the Banshee pistol delivers comparable energy in a package 11.5 inches shorter, optimized for dynamic movement and rapid target acquisition. Choose the Stevens for the deer stand; the Banshee for the defensive perimeter or patrol vehicle.

What does it weigh and what are the dimensions?

Unloaded, this pistol weighs 6.8 pounds (108.8 ounces), with an overall length of 28.5 inches from the end of the RipBrace to the muzzle threads. The critical dimension is the 10.5-inch 4140CM nitrided barrel, which dictates both its ballistic performance and its legal status as a pistol under federal law when configured without a vertical foregrip. The EML9 handguard provides 9 inches of M-LOK real estate for accessory mounting, and the receiver extension accepts the proprietary RipBrace, which adds approximately 5.5 inches to the length of pull when fully extended.

Who is this NOT for?

This is not a beginner's firearm or a plinking toy. A shooter unfamiliar with the recoil impulse of a .338 ARC from a 10.5-inch gas system, or one unwilling to invest in specialized, often expensive ammunition, will find this platform punishing and costly to operate. It is also categorically not for anyone seeking to circumvent NFA regulations—this is a pistol, and attaching a stock or a vertical foregrip without proper tax stamp registration creates an illegal short-barreled rifle (SBR). If your use case is casual range days or affordable varmint control like the Stevens 334 in .243 Win, look elsewhere.

What's in the box?

You receive the complete CMMG Banshee MK4 pistol, one CMMG ZEROED linear compensator threaded 5/8x24, one 10-round .338 ARC AR-compatible magazine, and the necessary paperwork including a chamber safety flag and owner's manual. Note that Ironclad Armory does not include optics, slings, or additional magazines as standard; these are critical mission components you must source separately. The pistol ships in a hard case, secured with foam, meeting all federal shipping requirements for direct delivery to your FFL of choice.

Is the CMMG Banshee MK4 .338 ARC worth it at $1517.99?

At this price point, it is a justified investment for a specific user: someone who requires a compact, heavy-hitting platform and understands the associated logistical and regulatory overhead. You are paying for the billet and forged 7075-T6 aluminum construction, the tuned gas system for a potent cartridge from a short barrel, and the integrated RipBrace system—features absent from budget AR builds. Compared to sourcing parts and building a similar .338 ARC pistol yourself, this offers a tested, warrantied system out of the box. If your needs are met by a more conventional sporting shotgun like the Stevens 555, this represents unnecessary complexity and expense.

Key attributes

upc	840442506582
manufacturer	CMMG
manufacturer part number	34A390F-AB
action	Semi-Auto
barrel length	10.5"
caliber/gauge	.338 ARC
capacity	10
color	Black
model	Banshee
product type	AR
safety	Ambidextrous
shipping weight	9.505
sights	Optics Ready

Frequently asked questions

Does this work with a standard AR-15 .308 Win lower receiver?: No, it does not. The .338 ARC cartridge, while based on a modified 6.5 Grendel/7.62x39 case head, requires a specific magazine and bolt face. This pistol uses a dedicated .338 ARC bolt and barrel, and is designed around Magpul PMAG .338 ARC magazines or similar. Do not attempt to use .308 Win/7.62 NATO magazines or bolts.
Is the RipBrace adjustable for length of pull?: Yes, the CMMG RipBrace features a telescoping design with multiple positive lock positions, offering approximately 3 inches of adjustable length of pull. It extends via a push-button release similar to many collapsible stock mechanisms, providing a stable contact point against the arm without constituting a 'stock' under current ATF guidelines (subject to change).
How long does shipping to my FFL take?: Ironclad Armory processes and ships in-stock firearms within 2 business days. Transit time via FedEx or UPS 2-Day Air is typically 3-5 additional business days to your chosen licensed dealer. You will receive tracking information once the item is scanned by the carrier. All shipments require an adult signature at the FFL.
Can I mount a suppressor on the 5/8x24 threads?: Absolutely. The 5/8x24 muzzle thread is the standard for .30 caliber and larger suppressors. You can direct-thread a compatible suppressor or use a muzzle device like a brake or flash hider that accepts a quick-detach suppressor mount. Ensure your suppressor is rated for the pressure and caliber of .338 ARC from a 10.5-inch barrel, as some .30 cal models have minimum barrel length restrictions.
What is the warranty period?: CMMG, the original manufacturer, provides a limited lifetime warranty to the original purchaser against defects in materials and workmanship. Ironclad Armory facilitates the warranty process but does not offer a separate warranty. Keep your original sales receipt for proof of purchase. Warranty service typically requires a return authorization and takes 2-4 weeks for turnaround.

Sources & methodology. Editorial review and rating by Declan Vance based on hands-on testing notes and published vendor specifications. Pricing verified at time of publication. Last fact-checked 2026-05-28.