Description

Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only

If you are looking to build a custom AR-15 from the ground up, the Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only gives you a solid, no-nonsense foundation. This is the same platform trusted by hobbyists and builders who want to finish their own receiver at home without a serialized paper trail. It is an 80% lower, meaning the critical fire control cavity is not yet fully machined, leaving the final steps in your hands. At a price point that makes sense for a budget-conscious build, this receiver delivers real value without cutting corners on the core design.

The Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is made from reinforced polymer, which keeps it lightweight while still holding up to the rigors of range time and field use. Unlike some cheaper lowers, this one features a metal-reinforced trigger pocket and buffer tower, so you get the strength you need where it matters most. The Rhino series also incorporates an integrated trigger guard and a flared magazine well for easier reloads, making it a practical choice for both first-time builders and experienced gun owners.

Overview

The RL556V3 is the third generation of Polymer80’s popular 80% lower design. It comes as a raw, unpainted receiver that requires some basic DIY work to complete: drilling the trigger and hammer pin holes, milling out the fire control pocket, and finishing the safety selector area. You do not need a CNC machine—just a drill press or a hand drill with a jig kit (sold separately). The Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is compatible with standard AR-15 LPKs and buffer tubes, so you can pair it with nearly any mil-spec parts you already have.

Features & Specs

• Material: High-impact, glass-reinforced polymer with stainless steel trigger and hammer pin inserts for wear resistance.
• Compatibility: Accepts all standard AR-15 lower parts kits, buffer tubes, and pistol grips. Works with both rifle and pistol calibers using appropriate uppers.
• Design Details: Integrated trigger guard, flared magwell for faster reloads, and a reinforced rear takedown pin boss to prevent cracking.

This receiver is also compatible with most aftermarket triggers, though we recommend sticking with mil-spec or drop-in cassette triggers for the smoothest installation. The polymer body keeps the overall weight of your build down without sacrificing the structural integrity you need for reliable cycling. The RL556V3 is a true 80% receiver, so it is not a finished firearm—you will need to complete the machining yourself.

Who It’s For

This lower is ideal for the hands-on builder who enjoys the process of finishing a receiver themselves. If you are someone who already has a drill press or a jig and wants to save money by skipping the serialized receiver route, the Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is a natural fit. It is also a solid option for those who want to experiment with different calibers or build a spare lower to keep on hand. Beginners can use it too, but you will need a good jig and some basic mechanical confidence to get it right. This is not a drop-in part—it is a project, and that is exactly the point.

Shipping & FFL

Because the Polymer80 RL556V3 – Rhino 80% AR15 Lower Receiver Only is not a finished firearm, it ships directly to your doorstep without the need for an FFL transfer. No background check is required at the time of purchase. However, please check your local and state laws before ordering, as some jurisdictions restrict or regulate 80% receivers. Once you complete the machining, the receiver becomes a firearm, and you are responsible for complying with all applicable laws regarding possession, use, and transfer. We recommend consulting with a local gunsmith or legal professional if you have any questions about your specific situation.