Description
You’ve built a dozen ARs from stripped lowers. You’ve chased the perfect fit, the zero-play connection, the trigger that breaks like glass. Now imagine that quest ending the moment you open the box. The Knights Armament SR-15 Lower Receiver Complete Assembly 223/5.56, Black, Magpul SL-S Stock is that destination. It’s a fully assembled, precision-engineered lower receiver from one of the most respected names in the tactical firearms industry, designed to mate perfectly with your SR-15 or compatible Mil-Spec upper and deliver immediate, reliable performance. This isn’t a parts kit; it’s a complete foundation, ready for your upper receiver and priced at $817.79.
When it comes to home defense or duty-ready builds, the lower receiver is the heart of the system. It houses the fire control group, dictates ergonomics, and ensures every critical interface—from the buffer system to the magazine well—functions under stress. Knights Armament doesn’t just meet Mil-Spec; they refine it. Their proprietary E3 bolt and enhanced fire control group are integrated here, offering a smoother, more reliable cam path and a crisp, consistent trigger pull right out of the gate. The assembly fits out of the box with SR-15 uppers and is engineered for exceptional compatibility with other Mil-Spec AR-15 upper receivers, eliminating the slop and tolerance stacking that plagues lesser builds. The included Magpul SL-S stock isn’t an afterthought—it’s a purpose-driven choice, offering a solid cheek weld and quick length-of-pull adjustments for rapid shouldering in confined spaces.
Let’s talk about what you’re actually getting. The core is the forged 7075-T6 aluminum SR-15 lower receiver, featuring the ambidextrous magazine release and bolt catch/release that KAC is famous for. This isn’t just left-hand friendly; it’s efficiency-driven, allowing for faster reloads and malfunction clearance from any shooting position. The installed E3 fire control group provides a clean, single-stage break that enhances control. The complete assembly, with its 6-position Magpul SL-S stock and H2 buffer system, is built for the sustained reliability demanded by professionals. At a weight of approximately 2.8 lbs as configured, it balances robustness with manageable heft.
Specifications
| Manufacturer | Knights Armament Company (KAC) |
| Model | SR-15 Complete Lower Assembly |
| Caliber | 223 Remington / 5.56x45mm NATO |
| Receiver Material | Forged 7075-T6 Aluminum |
| Stock | Magpul SL-S (6-Position) |
| Fire Control Group | KAC E3 Enhanced Trigger |
Pros: Unmatched out-of-the-box reliability and fit from a tier-one manufacturer. Includes KAC’s proprietary, highly-regarded E3 bolt system and enhanced trigger. Ambidextrous controls increase operational versatility. The Magpul SL-S stock offers superior stability. Saves significant time and gunsmithing guesswork.
Cons: The premium price point reflects its pedigree. Proprietary E3 bolt means you must use KAC-specific bolt carriers or complete uppers for full system synergy. It’s an investment in a foundation, not a complete rifle.
So who is this for? It’s for the shooter who understands that reliability is a feature you build in, not add on. It’s for the Missouri-based enthusiast building a no-compromise duty or defensive rifle who wants a proven, professional-grade lower without the assembly hassle. It’s also for the owner of a KAC SR-15 upper seeking the correct, factory-matched lower for optimal performance. This assembly is available at firearms-missouri.com for Missouri residents and nationwide, connecting you directly with this benchmark component.
Frequently Asked Questions
Q: Is this lower compatible with any standard AR-15 upper receiver?
A: It is designed for optimal fit and function with Knights Armament SR-15 uppers, which use a proprietary barrel extension and bolt for enhanced reliability. While it will physically mate with most Mil-Spec AR-15 uppers, to utilize the included E3 bolt, you need a KAC SR-15 upper or a barrel with a KAC-specific barrel extension.
Q: Does the price include the Magpul stock and all internal parts?
A: Yes. The $817.79 price is for the complete assembly as described. It includes the lower receiver, Magpul SL-S stock, buffer tube assembly with an H2 buffer, the enhanced KAC E3 fire control group (trigger, hammer, disconnector), ambidextrous controls, and a pistol grip. It ships ready for your upper receiver.
Q: What is the process for purchasing this?
A: As a complete lower receiver assembly, it is classified as a firearm. Purchase requires shipment to your local Federal Firearms License (FFL) holder, where you will complete a background check and transfer paperwork before taking possession. We facilitate this process seamlessly.
Ready to anchor your next build with uncompromising quality? Configure your upper and place your order for the SR-15 foundation.
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