Polymer80 80% Lower Receiver and Jig Kit (LR-308) – .308

Product Overview

The Polymer80 80% Lower Receiver and Jig Kit for the LR-308 platform represents a significant evolution in the world of modern sporting rifle customization. Designed for the experienced firearms enthusiast and builder, this kit provides the foundational component for constructing a lightweight, semi-automatic rifle chambered in .308 Winchester/7.62x51mm NATO. At its core, this is an unfinished “80% lower receiver,” meaning it is not classified as a firearm and can be legally completed by the end-user for personal use, following all applicable federal, state, and local laws. The Polymer80 LR-308 kit is engineered specifically for builders seeking to dramatically reduce the overall weight of their DPMS-pattern AR-10 build without sacrificing critical functionality.

Key Features

• Ultralight Polymer Construction: Weighing in at less than half a pound, this receiver tackles the traditional heaviness of the .308 AR platform head-on, enabling a more maneuverable and balanced final build.
• DPMS-Pattern Compatibility: Designed to work with standard DPMS-pattern .308/AR-10 parts kits, upper receivers, and magazines, ensuring broad compatibility and straightforward sourcing of components.
• Integrated Jig System: The included precision-machined jig is engineered to guide the user through the completion process, providing the necessary templates and drill bushings for proper fire control group pocket and pin hole machining.
• Reinforced High-Stress Areas: Critical zones, such as the buffer tower, takedown pin holes, and pistol grip screw location, are fortified with embedded metal reinforcements and advanced polymer engineering for enhanced durability.
• Stripped Weight, Not Strength: Polymer80 utilizes a high-performance, fiber-reinforced polymer that maintains structural integrity for reliable operation while achieving its groundbreaking weight reduction.
• Requires Machining for Completion: This is a project for the hands-on builder. Completion requires access to a drill press or hand tools, a router, and a basic understanding of machining processes to finish the fire control cavity.

Performance & Applications

The primary application of the Polymer80 LR-308 lower is to serve as the cornerstone for a custom, lightweight long-range or hunting rifle. By shedding significant weight from the lower receiver—typically the heaviest metal component—builders can reallocate that weight budget to other areas like optics, barrels, or suppressors without creating an overly burdensome system.

For the hunter, this translates to a .308 platform that is easier to carry over long distances in the field, reducing fatigue and improving mobility in challenging terrain. The reduced weight also benefits the practical marksman or competition shooter focused on dynamic shooting disciplines, where quick transitions and off-hand shooting are paramount. It enables the construction of a soft-recoiling, large-caliber rifle that handles more like a mid-weight AR-15, making extended training sessions more manageable and less taxing.

About Polymer80

Polymer80 is a recognized innovator in the firearms component industry, specifically known for pioneering the modern 80% receiver market. Their expertise lies in advanced polymer formulations and precision engineering, challenging the notion that polymer frames are unsuitable for high-stress applications. The company invests heavily in research, development, and real-world testing to produce components that meet rigorous performance standards. The “Warthogg” LR-308 lower is a direct result of this focused R&D, applying years of proven experience with polymer AR-15 lowers to the more demanding .308 platform. Their approach is grounded in material science and functional design, not marketing hype, which has earned them a reputation for serious products among knowledgeable builders.

Why Buy From Imbert Smither Arms

Located in San Carlos, CA, Imbert Smither Arms operates with a focus on providing specialized components to the builder community. We understand the technical nuances of projects like completing an 80% lower and stock products that meet a specific, practical need. Our selection is curated, favoring items that offer genuine innovation or utility. When you order from us, you are dealing with a source that comprehends the product’s application, ensuring you receive the correct components and necessary information for a compliant and successful build.

Make Your Decision

The Polymer80 LR-308 80% Lower and Jig Kit is a specialized tool for a specific builder: one who prioritizes weight reduction and is prepared for the hands-on completion process. It is not a generic part but a calculated engineering solution to a known challenge in the AR-10 platform. If your goal is to build a uniquely lightweight, custom .308 rifle and you possess the tools, skills, and commitment to complete the project safely and legally, this kit provides a proven and innovative starting point. Evaluate your needs, workshop capabilities, and local regulations to determine if this is the right foundation for your next build.

Technical Specifications

Manufacturer	Polymer80
Caliber	.308
Action Type	semi-automatic
Frame Material	polymer

Frequently Asked Questions