Description
The ATI Mil Sport AR-15 Stripped Lower Flat Cobalt Cerakote, Multi Cal is the foundational component for building a custom AR-15 rifle or pistol. This is a stripped lower receiver, meaning it arrives without the internal fire control group (trigger, hammer, disconnector) or stock assembly. It’s the serialized part, legally the firearm, and serves as the core platform you build upon. Finished in a durable Flat Cobalt Cerakote, it’s designed for compatibility with standard mil-spec AR-15 parts, offering a reliable and affordable starting point for your next build. At $48.21, it represents a significant value for a serialized receiver with a professional-grade finish.
Key Features
- Flat Cobalt Cerakote Finish: Provides superior corrosion resistance and a consistent, tactical matte finish that stands up to hard use and the elements.
- Multi-Caliber Marking: Officially marked “Multi Cal,” giving you the legal flexibility to build your upper receiver in 5.56 NATO, .300 Blackout, 6.5 Grendel, or other compatible AR-15 calibers.
- Mil-Spec Design: Engineered to strict military specifications for dimensional compatibility, ensuring it works with the vast ecosystem of aftermarket AR-15 components.
- Stripped & Ready for Customization: Arrives as a blank canvas, allowing you to select your exact preferred trigger, safety selector, bolt catch, and other internal parts to match your intended use.
Specifications & Details
| Material: | 7075-T6 Aluminum Forging |
| Finish: | Flat Cobalt Cerakote (H-190) |
| Caliber Marking: | Multi Cal |
| Compatibility: | Mil-Spec AR-15 Components |
| Fire Control Pocket: | Machined for Semi-Auto |
| Thread Size: | Standard 1/2″-28 Buffer Tube |
This lower is forged from 7075-T6 aluminum, the same high-strength alloy used in military and aerospace applications. The forging process creates a dense, durable receiver that can handle the stresses of sustained fire and hard use. The critical fire control pocket and pin holes are precision CNC-machined to ensure all your drop-in parts—from a basic mil-spec trigger to a high-end Geissele or LaRue unit—fit out of the box. That said, remember that FFL transfer required for firearm purchases applies to this item, as it is the serialized firearm component.
Who This Lower Is For
This is for the builder who sees a rifle as a project. It’s for the shooter who wants a home defense tool configured exactly to their layout—specific trigger pull, specific safety, specific stock. It’s for the hunter wanting a lightweight .300 Blackout build for suppressed use in Missouri’s timber. It’s also for the budget-conscious marksman seeking a no-frills, reliable foundation for a range or training rifle. If you have a specific vision for your AR’s ergonomics and performance, starting with a stripped lower like this is the only way to go.
Pros & Cons
Pros: The primary advantage is customization. You control every part that goes into it. The Cerakote finish is far more durable than standard anodizing, protecting against scratches and corrosion. The mil-spec compatibility means you’re not locked into a proprietary parts ecosystem. And the price point is compelling for a forged receiver with this level of finish.
Cons: It’s not a complete firearm. You must source and install all other parts, which requires tools, knowledge, and additional investment. For a first-time builder, the process can be daunting. There’s also the inherent responsibility—ensuring the final assembly is safe and functional rests entirely on you.
Frequently Asked Questions
Q: What parts do I need to complete this into a functioning firearm?
A: You will need a Lower Parts Kit (LPK), which includes the trigger, hammer, disconnector, safety selector, magazine release, bolt catch, and pivot/takedown pins. You also need a buffer tube kit (buffer tube, spring, buffer, castle nut, end plate) and a stock or pistol brace. Finally, you must pair it with a complete upper receiver assembly.
Q: Is this compatible with Palmetto State Armory (PSA) or Aero Precision upper receivers?
A: Yes. Since the ATI Mil Sport lower is built to standard mil-spec dimensions, it will mate correctly with virtually any mil-spec AR-15 upper receiver on the market, including those from major manufacturers like PSA, Aero Precision, BCM, and Daniel Defense. Fit may vary slightly between any two brands, but it should be within functional tolerances.
Q: Can I build this into a pistol, or does it have to be a rifle?
A: You can build it into either, as it is transferred as an “Other” firearm on the 4473. The initial build intent is crucial. If you first assemble it with a rifle-length barrel and stock, it must always remain a rifle. If you first build it with a barrel under 16″ and an arm brace (subject to current ATF rulings) or without a stock, it is a pistol. Plan your build path before you start.
Ready to start your custom build with a solid, value-priced foundation? This ATI Mil Sport lower is available at firearms-missouri.com for Missouri residents and nationwide.
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