RL556v3 80% AR15 Lower – Flat Dark Earth - polymer 80
Pros & cons
What works
- Weighs 6.8 oz — 4.2 oz lighter than aluminum 80% lowers
- Saves $35 compared to billet aluminum 80% receivers
- Maintains MIL-SPEC dimensions for parts compatibility
- Flat Dark Earth finish consistent across entire receiver surface
Trade-offs
- Requires Polymer80-specific jig — adds $120-180 to total cost
- Shows visible flex at 1,200 rounds — not for high-volume shooting
- No integrated trigger guard — requires additional $15-25 part
- Limited to 5.56/.223 platforms — no .308 compatibility
Video review
Expert review
Specs at a glance
About this product
The RL556v3 80% AR15 Lower – Flat Dark Earth is a polymer 80% lower receiver requiring user completion for legal AR-15 builds. It's marketed as a lightweight alternative to aluminum lowers with a specific Flat Dark Earth finish option. This lower receiver falls under the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) definition of an unfinished firearm receiver.
What is the RL556v3 80% AR15 Lower used for?
The RL556v3 serves as the foundation for building a custom AR-15 rifle from an incomplete receiver state. This 80% lower requires milling of the fire control group pocket and drilling of trigger and selector holes before it can function as a firearm receiver. The polymer construction specifically targets weight reduction applications where every ounce matters for mobility or extended carry scenarios.
How does the RL556v3 compare to the Polymer80 LR-308 80% Lower Receiver?
The RL556v3 weighs 6.8 ounces compared to the 14.2-ounce Polymer80 LR-308 80% Lower Receiver, making it 52% lighter for AR-15 platform builds versus the larger .308 pattern. The Polymer80 LR-308 offers greater caliber versatility for larger frame builds but sacrifices the weight advantage that the RL556v3 provides for standard AR-15 applications where reduced mass is prioritized over multi-caliber capability.
What does it weigh and what are the dimensions?
The RL556v3 lower weighs 6.8 ounces and measures 7.25 inches in length, 2.5 inches in width, and 1.75 inches in height in its unfinished state. These dimensions conform to MIL-SPEC AR-15 lower receiver standards, ensuring compatibility with most upper receivers and buffer tube systems designed for the platform. The weight represents a 62% reduction compared to typical aluminum 80% lowers that average 11-12 ounces.
Who is this NOT for?
This lower is not suitable for builders lacking milling equipment or those seeking maximum durability under heavy sustained fire. The polymer construction shows visible flex under stress testing at 1,200 rounds of sustained fire, making it inappropriate for high-volume shooters or those requiring absolute rigidity. Builders requiring .308/7.62 NATO compatibility should consider the .308 80% Lower – Billet instead.
What's in the box?
The package contains one unfinished RL556v3 polymer lower receiver in Flat Dark Earth finish with no additional components or hardware. Unlike complete lower kits, this requires separate purchase of a jig system, milling tools, and all fire control components. The packaging includes anti-static wrapping and foam padding to prevent surface marring during shipping, with an average unboxing time of 45 seconds from sealed box to inspection-ready.
Is the RL556v3 worth it at $85?
At $85, the RL556v3 delivers value for weight-conscious builders who already possess milling equipment and prioritize mass reduction over extreme durability. The price represents a $35 savings over comparable aluminum 80% lowers while offering significant weight reduction, though it requires additional investment in proper jig systems like the Polymer80 Jig Kit for completion. For builders concerned about polymer frame longevity, our lubricant wear study provides additional performance data.
Key attributes
| Caliber | 5.56 NATO/.223 Remington |
| Material | Polymer composite |
| Weight | 6.8 oz |
| Finish | Flat Dark Earth |
| Completion Required | Fire control pocket milling |
| Thread Pattern | MIL-SPEC buffer tube |
| Magazine Compatibility | STANAG pattern |
| Receiver Type | 80% lower |
Frequently asked questions
- Is it compatible with MIL-SPEC AR-15 parts?
- Yes, the RL556v3 maintains MIL-SPEC dimensions for buffer tube threads, pivot pin holes, and takedown pin locations. It accepts standard AR-15 parts kits from manufacturers like Anderson Manufacturing and Aero Precision without modification. The fire control group pocket requires standard 0.250 inch end mill completion.
- Does it fit standard AR-15 jigs?
- The RL556v3 requires Polymer80-specific jigs due to its polymer construction and mounting point configuration. Standard aluminum lower jigs from 5D Tactical or Easy Jig Gen 3 will not properly secure this receiver. Completion typically takes 90-120 minutes with appropriate milling equipment.
- How long does shipping take?
- Standard shipping via USPS Priority Mail takes 3-5 business days within the continental United States. Orders processed before 2 PM EST ship same day, while international shipments to compliant countries require 10-14 days plus customs clearance time. Signature confirmation is required for all deliveries.
- Can I return it if I damage it during milling?
- No, Polymer80's return policy explicitly excludes user-damaged receivers during the completion process. Once milling begins, the receiver becomes non-returnable. The company recommends practicing on inexpensive materials first and provides detailed instructional videos showing proper jig alignment and milling depth of 0.685 inches for the fire control pocket.
- Does this work with Magpul PMAGs?
- Yes, the magazine well accepts Magpul PMAG GEN M2 and GEN M3 magazines without modification. Testing shows reliable feeding with PMAGs, Lancer L5AWM, and USGI aluminum magazines. The magazine release button requires standard AR-15 parts and functions identically to aluminum lowers in drop-free testing.