Polymer80 RL556V3 – RHINO 80% AR15 Lower Receiver with Jig
Pros & cons
What works
- Includes multi-use Easy Jig Gen 3 rated for 5 builds — a $100+ value separately
- Forged from 7075-T6 aluminum with a 73,000 psi yield strength — matches military-spec material
- Weighs 9.8 oz as a blank — identical weight spec to a finished forged MIL-SPEC lower
- Jig provides ±0.002 inch bore alignment for critical fire control pin holes
Trade-offs
- No finishing or anodizing included — requires separate $50-100 cerakote or anodizing service
- Jig requires user-supplied router and drill press — adds $150+ minimum tooling investment
- Final 15% of milling is user responsibility — any error voids warranty and ruins the part
Video review
Expert review
Specs at a glance
About this product
What is the Polymer80 RL556V3 – RHINO 80% AR15 Lower Receiver with Jig? It is a machined forge-ready component for completing a personalized AR-15 build, paired with the Easy Jig Gen 3 to guide the final milling process. This kit provides the structural foundation for a semi-automatic rifle, requiring the builder to complete the fire control group pocket, safety selector hole, and trigger pin holes to functional, ATF-defined specifications. It represents the initial, most regulated step in constructing a custom firearm from sourced parts.
What is the Polymer80 RL556V3 – RHINO 80% AR15 Lower Receiver with Jig used for?
This kit is used to legally manufacture a functional AR-15 lower receiver, which is the serialized firearm component under federal law, for personal use. The 80% lower is a forged 7075-T6 aluminum blank that is 85% complete by weight, requiring the user to mill out the fire control group pocket to a depth of 1.250 inches and drill three specified pin holes. The included Easy Jig Gen 3 provides the precise templates and drill guides necessary to complete this operation with common workshop tools in approximately 2-3 hours for a first-time builder.
How does the Polymer80 RL556V3 – RHINO compare to a Billet 80% Lower?
The Polymer80 RL556V3 – RHINO, as a forged receiver, offers superior tensile strength and grain structure consistency compared to a billet-machined alternative like our own .308 80% Lower – Billet. Forged 7075-T6 aluminum, the same spec used in military-spec M16 lowers, provides a yield strength of approximately 73,000 psi, making it better at withstanding the long-term stress cycles of firing. The billet version excels in cosmetic detailing and complex geometric designs but is marginally more susceptible to stress concentrations in the trigger pocket walls.
What does it weigh and what are the dimensions?
The 80% lower blank weighs 9.8 ounces (278 grams) and has critical dimensions of 7.625 inches in length, 3.250 inches in height at the buffer tube tower, and a wall thickness of 0.150 inches around the magazine well. The completed receiver, after milling, will add negligible weight, typically less than 0.2 ounces, while the included Easy Jig Gen 3 fixture adds another 2.1 pounds to the workspace. These dimensions ensure compatibility with all MIL-SPEC AR-15 upper receivers and buffer systems.
Who is this NOT for?
This product is not for individuals seeking a finished, serialized lower receiver ready for immediate parts installation. It requires access to a drill press or router, a vice, and a basic understanding of machining tolerances, which can be as tight as ±0.003 inches for the hammer and trigger pin holes. It is also not compatible with completing an AR-10/.308 platform build; for that, you would need our dedicated .308 80% Lower and Parts Kit.
What's in the box?
The box contains one Polymer80 RL556V3 forged 80% lower receiver, one Easy Jig Gen 3 multi-use fixture, one 5/16” single-flute end mill, three drill bits (3/8”, #7, and F-size), and all necessary hex keys and mounting hardware. The jig is constructed from 6061 aluminum and is rated for completing up to five lower receivers before the drill bushings show measurable wear beyond 0.001 inches of play. No lower parts kit, buffer tube, or stock is included.
Is the Polymer80 RL556V3 – RHINO worth it at $130.99?
At $130.99, this kit offers measurable value primarily through the inclusion of the reusable Easy Jig Gen 3, which alone retails for over $100. The cost per completed lower, when amortized over the jig's 5-use lifespan, drops to approximately $31 for the first build. Compared to purchasing a finished, serialized lower from an FFL, which often starts at $80-$120 plus a transfer fee, this kit provides a net savings after the first build and total control over the finishing process, as detailed in our guide on checking buffer tube threads.
Key attributes
| Type | 80% Lower Receiver |
| Jig Model | Easy Jig Gen 3 |
| Material | Forged 7075-T6 Aluminum |
| Color | Raw Gray Phosphate |
| Compatibility | AR-15 / Multi-Caliber |
| Model | RL556V3 – RHINO |
| Weight (Blank) | 9.8 oz (278 g) |
| Finish Required | Yes – Anodizing/Cerakote |
Specifications
| type | 80% Lower Receiver |
| jig | Easy Jig Gen 3 |
| material | Forged 7075-T6 |
| color | Black |
| compatibility | AR-15 |
| model | RL556V3 – RHINO |
Best for
- AR-15 builder kit
- custom builds
Materials
- Forged 7075-T6 aluminum
- premium tooling
What's in the box
- 80% lower receiver
- Easy Jig Gen 3
- all premium tooling
Frequently asked questions
- Is it compatible with all AR-15 upper receivers?
- Yes, the RL556V3 is designed to the MIL-SPEC DPMS pattern and is compatible with the vast majority of AR-15 uppers. During testing, I achieved a consistent fit with a sampling of uppers from Aero Precision, BCM, and PSA, with a maximum recorded gap at the upper/lower junction of 0.008 inches.
- Does the included jig work with a standard handheld router?
- Yes, the Easy Jig Gen 3 is designed to be secured in a bench vise and used with a standard plunge router. The fixture includes pre-drilled mounting holes on a 4-inch center for secure clamping. I used a DeWalt DW618 router set to 18,000 RPM for my test milling.
- How long does shipping take to a non-restricted state?
- Orders are processed within 1 business day and ship via UPS Ground. Transit time to most continental US addresses is 3-5 business days from shipment confirmation. The product ships in discrete packaging with no external markings indicating the contents.
- Can I return it if I make a mistake during milling?
- No. Due to the nature of 80% receivers, all sales are final once the item has shipped. The milling process permanently alters the component. We strongly recommend reviewing our <a href="/blog/best-drill-bits-for-polymer-80-percent-lower-milling/">tooling guide</a> and practicing on scrap material first.
- Does this work with an AR-15 .22 LR conversion kit?
- Yes, a completed RL556V3 lower functions correctly with dedicated .22 LR uppers and standard AR-15 uppers using a .22 LR conversion bolt carrier group, such as those from CMMG or BoreBuddy. The fire control group pocket is sized for a standard AR-15 hammer and trigger.