Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only

If you are ready to build your own custom AR-15 from the ground up, the polymer80 rl556v3 – rhino 80% ar15 lower receiver only is the foundation you have been looking for. This is not a finished receiver; it is an 80% lower that requires you to complete the machining and assembly yourself. Polymer80 has built a solid reputation for making DIY firearm construction accessible, and the RL556V3 Rhino is their third-generation take on a lightweight, durable polymer lower. It is designed to work with standard mil-spec AR-15 upper parts kits and buffer tubes, giving you full control over the final build.

Overview

The polymer80 rl556v3 – rhino 80% ar15 lower receiver only is a polymer-based, unfinished lower that lets you legally manufacture your own firearm for personal use. It comes pre-jigged with integrated support for the included universal jig system, which means less guesswork during the drilling and milling process. The Rhino version features a reinforced front takedown pin boss and an integrated trigger guard, two upgrades that set it apart from earlier Polymer80 models. You will need to complete the fire control pocket, drill the trigger and hammer pin holes, and finish the safety selector detent channel before assembly.

Features & Specs

This receiver is built around the idea of simplifying the 80% build without sacrificing reliability. The polymer material is glass-filled nylon, which resists impact and holds up to repeated use. Below are the key details you need to know before starting your build.

• Manufacturer: Polymer80 | Category: Parts | Material: Glass-filled polymer with steel-reinforcement in high-stress areas
• Compatible with mil-spec AR-15 lower parts kits, buffer tube assemblies, and pistol grips (standard trigger guard already molded in)
• Includes: One RL556V3 Rhino 80% lower receiver, jig mounting blocks, and drill bit guide (jig frame and router bits sold separately)

If you are comparing this to other 80% lowers on the market, the Rhino stands out for its integrated rear takedown pin detent channel and the fact that it requires no special tools beyond a drill press and a router. The polymer80 rl556v3 – rhino 80% ar15 lower receiver only is also noticeably lighter than an aluminum lower, which is a plus if you are building a lightweight carbine or pistol.

Who It Is For

This lower is aimed at experienced builders who are comfortable with basic machining and who want a project that results in a fully functional, non-serialized firearm. It is not for first-time gun owners or people looking for a drop-in part. You should be confident in your ability to follow a jig guide and use a router safely. The polymer80 rl556v3 – rhino 80% ar15 lower receiver only is also well-suited for anyone who wants to experiment with different grip angles, trigger weights, or barrel lengths without buying a full factory lower. Because you are manufacturing your own firearm, there is no background check at the point of purchase, but you must be legally allowed to own firearms under federal and state law.

• DIY builders who want to learn the machining side of AR-15 assembly
• Hobbyists looking for a lightweight lower that accepts standard AR-15 parts
• Anyone who prefers a polymer lower over aluminum for reduced weight or corrosion resistance

Shipping & FFL

This product ships directly to your home address with no FFL transfer required at the time of purchase. Because the polymer80 rl556v3 – rhino 80% ar15 lower receiver only is not yet a finished firearm, it is not subject to standard firearm transfer regulations. However, you are responsible for ensuring that completing this receiver into a functional firearm is legal in your state and local jurisdiction. Some states and municipalities have specific restrictions on 80% lowers, including requirements for serialization or bans on unserialized receivers. Check your local laws before ordering. Once you complete the machining, the firearm must still comply with all federal and state laws regarding ownership and use.

• No FFL needed for delivery of the unfinished receiver
• You must be 18 or older to purchase (21 for handgun configuration)
• Final assembly and possession must comply with all applicable laws in your area