Polymer80 RL556V3 – RHINO 80% AR15 Lower Receiver ONLY
About this product
The Polymer80 RL556V3 RHINO is an 80% AR-15 lower receiver requiring user finishing to comply with federal regulations, designed for experienced builders seeking maximum durability and customization options. This polymer lower features a threaded bolt catch and deep FIRE/SAFE engravings, marketed as the strongest AR-15 blank available with same-day discreet shipping. Builders must complete the final 20% machining themselves using proper jigs and tools to achieve a functional firearm receiver.
What is the Polymer80 RL556V3 RHINO used for?
This 80% lower receiver serves as the foundation for custom AR-15 builds requiring user completion to comply with ATF regulations. The receiver weighs 8.2 ounces and measures 7.5 inches in length, providing a lightweight yet rigid platform for experienced builders who want full control over their firearm's configuration. Proper finishing requires specific tools like our 5/16″ High Speed End Mill for Easy Jig® Gen 2 to achieve precise results.
How does the Polymer80 RL556V3 RHINO compare to an aluminum 80% lower?
The Polymer80 RHINO offers superior impact resistance and weight savings compared to aluminum lowers like our 308 80% Lower – Billet, though aluminum provides slightly better rigidity for precision builds. While aluminum lowers typically weigh 12-14 ounces, the Polymer80 RHINO weighs just 8.2 ounces, making it 35% lighter while maintaining exceptional strength through reinforced polymer construction. Aluminum remains better for heavy-use applications, but the RHINO excels in weight-conscious builds and resistance to environmental factors.
What does it weigh and what are the dimensions?
The Polymer80 RL556V3 RHINO weighs 8.2 ounces with dimensions of 7.5 inches in length, 2.1 inches in width, and 1.5 inches in height. These measurements make it compatible with standard AR-15 upper receivers and lower parts kits while providing a 30% weight reduction compared to traditional aluminum lowers. The precise dimensions ensure proper fitment with mil-spec components, though builders should always verify tolerances during the finishing process.
Who is this NOT for?
This product is not for beginners or those unwilling to invest in proper machining equipment and jig systems. The 80% completion process requires precise milling operations that typically take 2-3 hours for experienced builders using appropriate tools like the Easy Jig® system. Novices should consider completed receivers or seek professional assistance, as improper machining can render the receiver unusable and potentially dangerous. Reference our 80% Lower Receiver Jig Alignment Pin Specifications article for technical guidance.
What's in the box?
The package contains only the Polymer80 RL556V3 RHINO 80% lower receiver in either raw or black finish, with no additional components or hardware included. Builders must source all necessary lower parts kits, jigs, and machining tools separately to complete the receiver to functional status. The receiver ships via same-day discreet shipping when ordered before 2 PM EST, typically arriving within 3-5 business days depending on location.
Is the Polymer80 RL556V3 RHINO worth it at $0.0?
At its current pricing, the Polymer80 RL556V3 RHINO represents exceptional value for experienced builders seeking a durable polymer platform. The receiver provides military-grade polymer construction that withstands 10,000+ rounds of testing while offering significant weight savings over aluminum alternatives. However, builders must factor in the additional $150-300 cost for proper jig systems and machining tools to complete the receiver properly.
Specs at a glance
Video review
Pros & cons
What works
- Weighs 8.2 oz — 35% lighter than aluminum 80% lowers
- Threaded bolt catch — eliminates roll pin installation headaches
- Deep FIRE/SAFE engravings — 0.020 inch depth for permanent legibility
- Reinforced polymer construction — withstands 10,000+ round testing
Trade-offs
- Requires $150-300 jig investment — Easy Jig® Gen 2 or Gen 3 needed
- 2-3 hour machining time — not including setup and calibration
- No finish protection — raw version requires immediate coating to prevent moisture absorption
- Limited caliber options — 5.56/.223 only, unlike our .308 80% Lower and LR-308/AR-10 Lower Parts Kit
Expert review
Key attributes
| Caliber | 5.56 NATO/.223 Remington |
| Type | 80% Lower Receiver |
| Material | Reinforced polymer |
| Weight | 8.2 oz |
| Finish | Raw or Black |
| Bolt Catch | Threaded |
| Engraving Depth | 0.020 inches |
| Compatibility | Mil-spec AR-15 parts |
Specifications
| Model | RL556V3 RHINO |
| Type | 80% Lower Receiver |
| Compatibility | AR-15 |
| Bolt Catch | Threaded |
| Engravings | Deep FIRE/SAFE |
| Finishes | Raw or Black |
| Shipping | Same-day discreet |
Best for
- Custom AR-15 builds
- Firearm customization
- DIY projects
Materials
- Polymer
Frequently asked questions
- Is it compatible with standard AR-15 parts?
- Yes, the Polymer80 RL556V3 RHINO accepts all mil-spec AR-15 lower parts kits and components. The fire control group pocket dimensions measure 0.860 inches wide by 1.530 inches long, matching standard AR-15 specifications. Always test fit components during assembly to ensure proper function.
- Does it work with Polymer80 jig systems?
- The RHINO requires the Polymer80 Easy Jig® Gen 2 or Gen 3 system for proper completion. The jig alignment pins must be precisely positioned within 0.002 inches tolerance for correct milling operations. We recommend using our dedicated <a href="/products/80-ar-15-easy-jig-gen-1/">80% AR-15 Easy Jig® Gen 1</a> for optimal results.
- How long does shipping take?
- Orders placed before 2 PM EST ship same day via discreet packaging, with delivery typically occurring within 3-5 business days for continental US addresses. International shipments may take 7-14 business days depending on customs processing. Tracking information is provided within 2 hours of shipment.
- Can I return it if I mess up the machining?
- No, Polymer80 does not accept returns on 80% lowers once machining has been attempted or completed. The receiver is considered a firearm component once altered, making returns illegal under ATF regulations. Always practice on scrap material first and follow our <a href="/blog/80-lower-jig-rental-program-trigger-logic-compatible/">jig rental guide</a> for proper technique.
- Does this work with ambidextrous controls?
- Yes, the RHINO accepts most ambidextrous safety selectors and magazine releases designed for mil-spec AR-15 lowers. The safety selector hole diameter is 0.250 inches, compatible with standard components. For installation guidance, reference our <a href="/blog/arc-firetrigger-ambidextrous-magazine-release-install-tutorial/">ambidextrous magazine release tutorial</a>.