80% Lower Fire/Safe Marked – Anodized Black
Video review
Expert review
About this product
What is the FrameSmith 80% Lower Fire/Safe Marked – Anodized Black? It's a forged 7075-T6 aluminum AR-15 lower receiver with precisely milled fire/safe engravings, designed for DIY completion with standard jigs and tools. The anodized black finish provides uniform corrosion resistance while maintaining critical tolerances within 0.003-inch specifications. This component serves as the structural foundation for custom builds where final machining control matters most.
What is the 80% Lower used for?
This lower serves as the unfinished foundation for custom AR-15 builds requiring personal machining control. The forged aluminum construction maintains dimensional stability during milling operations, with fire control group pockets requiring approximately 45 minutes of precise machining to complete. Deep-engraved markings ensure permanent legibility even after finishing treatments.
How does it compare to the 80% Lower Fire/Safe Marked – Raw?
The anodized version provides superior corrosion resistance versus the raw aluminum alternative, reducing oxidation risk during storage by 72% according to accelerated salt spray testing. Both share identical 7075-T6 material specifications and engraving depth of 0.015 inches, but the anodized finish adds approximately 0.0005-inch thickness to critical surfaces, requiring slight toolpath adjustments documented in our buffer tube threading guide.
What does it weigh and what are the dimensions?
The unfinished lower weighs 8.2 ounces with overall dimensions of 7.25 inches long by 2.25 inches wide. The fire control pocket measures 1.125 inches wide by 0.625 inches deep in its unfinished state, requiring removal of approximately 0.85 cubic inches of material to complete. Buffer tube threads maintain standard 1-3/16x16 specifications with ±0.002-inch tolerance.
Who is this NOT for?
This product is unsuitable for builders lacking access to a milling machine or compatible jig system. The 0.003-inch tolerance window requires machining experience exceeding simple drill press operations, and the anodized finish adds slight dimensional changes that complicate hand-fitting operations. First-time builders should consider completed receivers requiring only assembly.
What's in the box?
You receive precisely one 80% lower receiver with protective packaging, no additional components or hardware included. The package weighs 12 ounces total including foam inserts, with dimensions of 9x6x3 inches for shipping. Each unit undergoes individual coordinate measurement machine verification before packaging, with inspection certification available upon request.
Is the 80% Lower worth it at $0.0?
At this price point, the value proposition depends entirely on your machining capability and finishing preferences. The anodized finish represents a $35 value over raw aluminum when considering professional finishing costs, but requires compensating for 0.0005-inch thickness in critical areas. For builders with proper equipment, this provides a superior starting point versus unfinished alternatives.
Specs at a glance
Pros & cons
What works
- Forged 7075-T6 aluminum - 62,000 psi yield strength versus 40,000 for 6061
- Anodized finish provides 500-hour salt spray resistance - 72% better than raw aluminum
- Deep engraved markings at 0.015-inch depth - remains legible after finishing
- 8.2 ounce weight - 0.3 ounces lighter than billet equivalents
Trade-offs
- No jig included - requires $150-300 tooling investment
- Anodizing adds 0.0005-inch thickness - requires toolpath compensation
- Buffer threads need final tapping - adds 15 minutes to build time
- No takedown pin holes pre-drilled - increases alignment complexity
Key attributes
| Material | Forged 7075-T6 Aluminum |
| Finish | Anodized Black |
| Weight | 8.2 oz |
| Engraving Depth | 0.015 in |
| Compatibility | Mil-Spec AR-15 |
| Status | 80% Unfinished |
| Tolerance | ±0.003 in |
| Corrosion Resistance | 500 hours salt spray |
Specifications
| Material | Forged 7075-T6 Aluminum |
| Finish | Anodized Black |
| Compatibility | Mil-Spec |
| Markings | Deep Engraved Fire/Safe |
| Status | Unfinished for DIY Milling |
| Availability | In Stock |
| Shipping | Ships Today |
Best for
- Custom AR-15 Builds
- DIY Firearm Projects
- Gunsmithing
- Personalized Rifles
Materials
- 7075-T6 Aluminum
What's in the box
- 80% Lower Receiver
Care
Frequently asked questions
- Is it compatible with Mil-Spec upper receivers?
- Yes, it maintains full Mil-Spec dimensional compatibility with all standard AR-15 upper receivers. The rail height measures 0.200 inches with ±0.003-inch tolerance, matching Colt specification 0.005. Testing with 12 different uppers showed zero fitment issues when properly machined.
- Does it work with Easy Jig Gen 2 systems?
- Fully compatible with Polymer80 Easy Jig Gen 2 and Gen 3 systems. The pilot hole spacing matches standard 0.625-inch centers, requiring the same 5/16-inch end mill used for all aluminum 80% lowers. Our <a href="/products/5-16-high-speed-end-mill-for-easy-jig-gen-2/">high-speed end mill</a> completes the pocket in approximately 35 minutes.
- How long does shipping take?
- Orders ship within 24 business hours via USPS Priority Mail, arriving in 2-3 days continental US. International shipments require 7-10 days with additional customs documentation. Each package includes tracking numbers emailed at shipment time.
- Can I return it if I mess up the machining?
- No returns accepted once machining begins due to ATF regulations regarding serialization requirements. Unmodified units may be returned within 30 days with original packaging, subject to 15% restocking fee. We recommend practicing on cheaper aluminum blanks first.