Aero Precision STS AR-15 Stripped Lower Receiver, Black

Description

The Aero Precision STS AR-15 Stripped Lower Receiver, Black is the serialized foundation for building a custom AR-15 rifle or pistol. This is the part legally defined as the firearm, requiring an FFL transfer. It’s a high-quality, mil-spec compatible blank canvas machined from 7075-T6 aluminum, ready for you to install your chosen trigger, safety, stock, and grip to create a rifle tailored to your specific needs.

Key Features

• STS (Screw-Together System) Design: Utilizes threaded pins and set screws for the bolt catch and trigger guard, eliminating the need for roll pins and making assembly significantly easier with basic tools.
• 7075-T6 Aluminum Forging: Provides superior strength and durability compared to 6061 aluminum, meeting military specifications for hard use.
• Flared Magwell: The subtly widened magazine well opening allows for faster, more positive magazine insertion, especially under stress or in low-light conditions.
• Anodized Black Finish: A hard, durable Type III hardcoat anodizing protects the receiver from corrosion and wear, ensuring a long service life.
• Integrated Trigger Guard: The guard is part of the receiver forging, removing a potential weak point and simplifying the build process—no separate guard to install.

Specifications & Details

Material	7075-T6 Aluminum Forging
Finish	Type III Hardcoat Anodized, Black
Caliber Compatibility	Multi (5.56 NATO / .223 Rem, .300 BLK, etc.)
Thread Pattern	Standard AR-15 / Mil-Spec
Trigger Guard	Integrated, Flared
Magazine Compatibility	Standard AR-15 / STANAG

Weighing in at just under 8 ounces stripped, this receiver is the lightweight starting point for any build. Its design is mil-spec compatible, meaning it will accept the vast majority of aftermarket AR-15 parts kits, grips, and stocks without modification. This is crucial when you’re piecing together a reliable home defense tool and need to know your chosen Geissele trigger or B5 Systems stock will fit out of the box. The STS system is the real standout—here’s the thing—it turns a frustrating job requiring specialized punches into a straightforward task with an Allen wrench. For a price of $85.81, you’re getting Aero Precision’s renowned machining quality and a feature set that genuinely simplifies the building experience.

Who This Lower Receiver Is For

This stripped lower is for the builder who values precision engineering but wants to avoid the hassle of traditional roll pins. It’s for the Missouri shooter assembling a dedicated bedside rifle who needs absolute confidence in their foundation. It’s also ideal for first-time builders intimidated by the assembly process; the STS system provides a more forgiving and tool-friendly entry point. When it comes to building a patrol rifle or a competition gun where every second on a reload counts, that flared magwell offers a tangible advantage.

Pros & Cons

Pros: The STS pin system is a legitimate game-simplifier for assembly. The forged 7075-T6 aluminum is top-tier for strength. The integrated, flared trigger guard is both durable and functional. Aero Precision’s quality control and finish are consistently excellent. It provides a solid platform compatible with countless uppers from brands like BCM, Palmetto State Armory, and Aero’s own M4E1.

Cons: As a stripped receiver, it requires the purchase of a Lower Parts Kit (LPK), buffer system, stock, and grip—the initial cost is just the beginning. You must factor in the cost and process of an FFL transfer required for firearm purchases. Some purists may prefer the absolute rigidity of a fully machined billet receiver, though for 99% of applications, this forged unit is more than sufficient.

Frequently Asked Questions

Q: What tools do I need to complete this stripped lower?

A: With the STS system, you primarily need a set of Allen wrenches (hex keys), an armorers wrench for the buffer tube, and basic hand tools. The need for roll pin punches and a vise block is greatly reduced or eliminated, making it a more accessible project.

Q: Is this lower receiver compatible with .300 AAC Blackout uppers?

A: Yes, absolutely. The lower receiver itself is caliber-agnostic. It is designed for the multi-caliber AR-15 platform. You can pair it with an upper chambered in 5.56 NATO, .223 Remington, .300 BLK, 6.5 Grendel, and other cartridges that use the standard AR-15 lower footprint and magazine format.

Q: What is included when I purchase this?

A: You receive the single, serialized Aero Precision STS stripped lower receiver. It does not include any internal parts (fire control group, safety selector, magazine catch, etc.), buffer tube assembly, stock, or pistol grip. Those are purchased separately to complete your firearm. This item is available at firearms-missouri.com for Missouri residents and nationwide where permitted.

Ready to start your build with a foundation that simplifies the process? Select your FFL dealer at checkout to begin the transfer process for your Aero Precision STS lower.