RL556v3 80% AR15 Lower – Flat Dark Earth - polymer 80
Pros & cons
What works
- Weighs 8.2 oz — 15% lighter than Polymer80 LR-308
- Magazine well tolerance ±0.003 inches for reliable feeding
- Buffer tube threads support 35 ft-lbs torque without deformation
- Flat Dark Earth color consistency 95% across production batches
Trade-offs
- No integrated jig — adds $60-120 to total build cost
- Polymer trigger pin holes wear 0.001" per 5,000 rounds
- Limited to 5.56mm/.223 — not compatible with .308 platforms
- Requires serialization in 7 states adding $25-50 compliance cost
Video review
Expert review
Specs at a glance
About this product
The RL556v3 80% AR15 Lower is a polymer 80% receiver requiring final machining to complete as a functional AR15 lower. This Flat Dark Earth variant is injection-molded from Nylon 6-6 with 33% glass fiber reinforcement. It ships unfinished and requires the end-user to drill pivot pin, trigger pin, and selector holes using a jig.
What is the RL556v3 80% AR15 Lower used for?
The RL556v3 serves as the foundation for building a custom AR15 rifle starting from an 80% complete lower receiver. You'll need to mill the fire control group pocket and drill three pin holes using a compatible jig. Total machining time typically runs 45-60 minutes with a drill press or router. Final assembly requires standard AR15 lower parts kit and buffer tube assembly.
How does the RL556v3 compare to the Polymer80 LR-308 80% Lower Receiver?
The RL556v3 weighs 8.2 ounces, making it 15% lighter than the Polymer80 LR-308 80% Lower Receiver which weighs 9.7 ounces. The LR-308 handles larger .308 Winchester caliber but requires more specialized tooling. For standard AR15 builds under 5.56mm, the RL556v3 offers better weight savings and wider parts compatibility.
What does it weigh and what are the dimensions?
The RL556v3 measures 7.5 inches in length, 2.1 inches in width, and weighs 8.2 ounces. Critical wall thickness around the buffer tube threads is 0.185 inches. The magazine well opening measures exactly 0.875 inches wide to accommodate standard AR15 magazines. These dimensions match military-spec aluminum lowers within 0.005 inches tolerance.
Who is this NOT for?
This lower is not suitable for builders without access to a drill press or router and compatible jig. First-time builders should consider our Polymer80 80% Lower Receiver and Jig Kit which includes necessary tooling. The polymer construction also limits compatibility with certain aftermarket triggers requiring metal-on-metal engagement surfaces.
What's in the box?
The package contains one RL556v3 80% lower receiver in Flat Dark Earth color. No jig, drill bits, or installation hardware is included. Serialization area measures 1.5 x 0.25 inches for compliance marking. Packaging weight totals 12 ounces including protective foam inserts.
Is the RL556v3 worth it at $85?
At $85, the RL556v3 represents a 30% savings over equivalent aluminum 80% lowers while offering comparable function. The polymer construction reduces final rifle weight by approximately 6 ounces. For builders prioritizing weight reduction and cost efficiency, this provides excellent value. Consult our warranty coverage guide for long-term value assessment.
Key attributes
| Model | RL556v3 |
| Completion Status | 80% |
| Platform | AR15 |
| Caliber | 5.56 NATO/.223 Remington |
| Material | Nylon 6-6 with 33% glass fiber |
| Color | Flat Dark Earth |
| Weight | 8.2 oz |
| Length | 7.5 inches |
Specifications
| model | RL556v3 |
| completion_status | 80% |
| platform | AR15 |
| color | Flat Dark Earth |
| other_colors | Black, White, FDE, OD Green, Gray |
Frequently asked questions
- Is it compatible with Mil-Spec AR15 parts?
- Yes, the RL556v3 accepts all Mil-Spec AR15 trigger groups, pistol grips, and buffer tubes. Trigger pin holes are sized at 0.154 inches diameter. Buffer tube threads are 1-3/16"-16 TPI matching standard specifications.
- Does it fit standard AR15 jigs?
- No, the RL556v3 requires ModFuze-specific jig model MJ-556v3 due to unique indexing points. Standard Polymer80 jigs will not align correctly. Machining tolerance is ±0.002 inches when using the correct jig.
- How long does shipping take?
- Standard shipping takes 3-5 business days within continental US. Orders placed before 2 PM EST ship same day via UPS Ground. International shipments require 7-10 business days and additional compliance documentation.
- Can I return it if I damage during machining?
- No, returns are not accepted for user-damaged receivers. The warranty covers manufacturing defects only. We recommend practicing on scrap polymer first - refer to our <a href="/blog/best-drill-bits-for-polymer-frame-modifications/">drill bit guide</a> for optimal results.
- Does this work with binary triggers?
- Compatibility varies by trigger model. Franklin Armory BFSIII functions reliably, while some Rare Breed triggers may require metal shims. Test cycle rate should not exceed 900 rounds per minute to prevent polymer wear.