Description
The Rock River Arms Complete Lower Half, 5.56/223 Standard Trigger, CAR Stock is a fully assembled AR-15 lower receiver, ready to be paired with a compatible upper receiver to build a functional rifle. It includes the stock, trigger group, and all lower parts, requiring no additional assembly. This unit is drop-in ready and ships to Missouri and compliant US states.
Key Features
- Complete & Ready to Go: Comes fully assembled with a standard single-stage trigger, CAR-style collapsible stock, pistol grip, and all necessary lower parts. No need to source small pins or springs.
- Budget-Friendly Foundation: At $258.36, this represents a solid value for a complete, reputable-brand lower, saving you the time and potential hassle of a parts kit build.
- Mil-Spec Compatibility: Built to standard AR-15 specifications, ensuring wide compatibility with the vast majority of AR-15 upper receivers on the market from brands like Palmetto State Armory, Aero Precision, and BCM.
- Classic CAR Stock: Features a lightweight, six-position collapsible CAR stock, offering a proven design for adjustability and a classic look.
Specifications & Details
| Specification | Detail |
|---|---|
| Manufacturer | Rock River Arms |
| Caliber Compatibility | 5.56 NATO / .223 Remington |
| Trigger | Standard Single-Stage |
| Stock | 6-Position Collapsible CAR |
| Receiver Material | 7075-T6 Aluminum (Forged) |
| Finish | Hardcoat Anodized |
This lower is built on a forged 7075-T6 aluminum receiver, the same material used in military-specification rifles, providing a durable and lightweight foundation. The hardcoat anodized finish offers excellent corrosion resistance. Weighing in at approximately 2.5 lbs as configured, it provides a balanced feel when mated with a complete upper. The included standard trigger is a practical, reliable component—it’s not a match-grade unit, but it gets the job done for general use and plinking, which is the whole point of a value-focused build.
Who This Lower Is For
This Rock River Arms lower is ideal for the first-time builder who wants to avoid the complexity of assembling a lower from scratch. It’s also a smart pick for the budget-conscious shooter looking for a reliable, no-frills foundation for a spare-parts or “beater” upper. If your goal is a straightforward, functional AR-15 for the range without a hefty investment, this lower delivers the core components you need. That said, if you’re chasing ultra-lightweight builds or require a specific high-end trigger out of the gate, you’ll likely want to start with a stripped receiver.
Pros & Cons
Pros: The primary advantage is convenience and value—you get a complete, quality-assembled lower from a trusted manufacturer at a competitive price point. It’s genuinely mil-spec compatible, so finding a matching upper is simple. The CAR stock is a timeless, functional choice. You save both money and time compared to buying all the components separately.
Cons: The standard trigger is perfectly serviceable but basic; enthusiasts may want to upgrade it later. The CAR stock, while classic, lacks some of the modern cheek weld and storage features of newer models. Look, it’s a foundational piece—you’re not getting premium bells and whistles, but you are getting a solid start.
Frequently Asked Questions
Q: Is this considered a firearm, and how do I purchase it?
A: Yes, the lower receiver is the legally controlled firearm component. Purchasing requires shipment to a licensed FFL dealer, where you will complete a background check and paperwork before taking possession. FFL transfer required for firearm purchases is standard procedure.
Q: What else do I need to build a working rifle?
A: You will need a complete AR-15 upper receiver assembly (barrel, handguard, bolt carrier group, charging handle) and a magazine. That’s it. Simply join the two halves with the takedown pins, and the rifle is functional.
Q: Will this lower work with a .300 Blackout or other caliber upper?
A: Absolutely. While marketed for 5.56/.223, this lower will function perfectly with uppers in calibers like .300 Blackout, 6.5 Grendel, and others that use a standard AR-15 lower footprint and magazine well. Always confirm magazine compatibility for your chosen caliber.
For a straightforward, reliable start to your next AR-15 project, this complete lower from Rock River Arms offers proven performance without complicating the process. See if it’s the right foundation for your build at firearms-missouri.com.



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