Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only

If you are building an AR-15 from the ground up and want a solid foundation that puts the work in your hands, the Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is a strong starting point. This isn’t a finished, serialized component. It is an unfinished 80% lower, meaning you complete the machining and finishing steps yourself to create a functional firearm frame. For those who enjoy the build process, this blank gives you a clean, modern platform to work with, built around Polymer80’s well-known Rhino design. Keep reading to see if this lower fits your next project.

Overview

The Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is an unfinished polymer receiver designed for the DIY builder. It comes as a raw 80% blank, meaning the critical fire control cavity and trigger pocket are not fully machined. You will need to complete those steps at home using standard jigs and tooling. The Rhino series features an integrated trigger guard and a reinforced rear takedown lug area, which adds durability where the lower sees the most stress. This blank is compatible with standard mil-spec AR-15 upper receivers and parts kits. If you are looking for a hands-on project that results in a custom rifle, this is a practical choice.

Features & Specs

• 80% Completion State: The RL556V3 arrives as an unfinished lower. You must mill out the trigger pocket, drill the selector and hammer pin holes, and finish the fire control cavity yourself. No serial number is present, so no FFL transfer is required for the blank itself.
• Rhino Integrated Design: The Rhino V3 includes a molded-in trigger guard and a reinforced rear lug. The polymer is glass-filled nylon, which provides a good balance of weight savings and impact resistance for a range build or truck gun.
• Milspec Compatibility: This lower accepts standard AR-15 upper receivers, buffer tubes, grips, and trigger groups. You can use common jig systems like the Polymer80 jig or third-party alternatives to complete the machining.

The Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is essentially a blank canvas. It does not include a jig, bits, or any finishing tools. You will need to supply those separately. The polymer material is lighter than aluminum, which can be a plus if you are building a lightweight carbine. The integrated trigger guard eliminates one extra part installation step after finishing.

Who It’s For

This lower is for the builder who wants to learn the internal layout of an AR-15 platform by hands-on machining. It is not for someone looking for a drop-in, ready-to-use receiver. If you have experience with a drill press, router, or hand files, and you are comfortable following detailed instructions, the RL556V3 is a good project. It is also suited for shooters who want to build a firearm specifically for their own use without relying on a serialized, factory-made receiver. Because it is an 80% blank, you are responsible for the final fit and function. If you enjoy tinkering, customizing, and understanding every part of your rifle, this lower makes sense.

Shipping & FFL

Because the Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is sold as an unfinished 80% blank, it is not classified as a firearm under current federal regulations. It can be shipped directly to your doorstep without going through a Federal Firearms License (FFL) dealer. However, please check your local and state laws before ordering. Some states and municipalities restrict or prohibit the possession of unfinished receivers, 80% blanks, or unserialized firearm components. It is your responsibility to ensure compliance with all applicable laws. Once you complete the machining and make it functional, you are required to comply with all federal, state, and local regulations regarding firearm possession and use. We do not provide legal advice, so verify your local laws before purchase.