Ruger AR-15 Stripped Upper Receiver - Mil-Spec 7075-T6 Forged Aluminum, Type III Hard-Coat Anodized Finish, M4 Feed Ramps, Black - 91004
Product Description
Building a top-tier modern sporting rifle, high-accuracy tactical carbine, or specialized custom caliber platform requires an upper receiver hub manufactured to precise dimensional standards. Loose commercial tolerances often lead to bolt carrier group friction or handguard alignment shifts on the bench, while low-grade castings can flex under heavy firing schedules. The **Ruger® AR-15 Stripped Upper Receiver (91004 / 736676910045)** completely flatlines these assembly bottlenecks, delivering a premium **7075-T6 forged aluminum core** machined straight from factory blueprints.
Proudly forged and precision-milled in the United States by Sturm, Ruger & Co., this clean, factory-original stripped upper is structured to standard military specifications. It features a deep, non-reflective **Type III Class 2 hard-coat anodized finish** that protects the underlying alloy against field scrapes and corrosive bore solvents. Designed workspace-ready for custom parts configurations, the receiver includes pre-cut **M4 feed ramps** to ensure reliable, smooth cartridge feeding, along with native machined channels for a standard forward assist and spring-loaded ejection port door assembly. This rugged component provides a flawless foundation right from your armorer workbench.
Engineered to pin seamlessly onto standard mil-spec lower receivers, this factory-calibrated stripped upper ensures absolute structural alignment directly from your workspace bench.
*Armorer Bench Notes & Real-World Receiver Custom Staging Guidance: The Ruger 91004 components pack arrives workspace ready, securely wrapped in factory-original anti-static poly inventory shielding. NATIVE MIL-SPEC FORGED INTERFACE MATRIX: This stripped flat-top receiver shell is engineered natively, strictly, and precisely to accept **standard AR-15 upper receiver completion parts and barrel extensions**. *Host Barrel Extension Alignment Checklist:* The interior extension tunnel features precision-milled M4 feed ramp cuts, meaning it should be paired with a **barrel extension that also features matching M4 feed ramps** on your bench to guarantee reliable extraction tracking. Armorer Workbench Custom Staging Sequence: 1. Visually confirm your workbench is clean and equipped with a dedicated AR-15 upper receiver vise block or clamshell fixture tool to protect the exterior finish from clamping stress. 2. Apply a thin layer of premium anti-seize lubricant or high-pressure molybdenum disulfide grease to the external receiver nose threads before threading on a custom barrel nut. 3. Utilize an appropriate armorer barrel wrench to torque your barrel assembly to the proper specification—strictly between 35 and 80 foot-pounds—ensuring a gas tube alignment notch aligns perfectly over the top path. 4. Slide in a standard forward assist plunger assembly from the rear right port, tapping the retention roll pin gently home with a non-marring starter punch. 5. Position your ejection port cover spring and door hinge pin horizontally through the receiver lugs, locking the assembly down with a standard C-clip token. 6. Slide your chosen mil-spec bolt carrier group and charging handle into the rear tracking lanes to confirm perfectly smooth, friction-free cycling parameters before headspacing and running performance tests downrange.*
Key Features
- Premium Forged 7075-T6 Aluminum: Forged from high-tensile 7075-T6 structural aluminum alloy, providing significantly greater structural strength and fatigue life than weaker 6061 variants.
- Type III Hard-Coat Anodized Shell: Coated in an ultra-durable, thick hard anodized layer that seals the aluminum against field scratches, sweat corrosion, and harsh bore solvents.
- Factory Milled M4 Feed Ramps: Features pre-cut, extended M4 feed ramps to ensure reliable double-stack cartridge feeding under rapid-fire operation downrange.
- Standard Picatinny Flat-Top Rail: Equipped with a full-length top Picatinny rail section featuring crisp alignment channels for mounting red dots, LPVO mounts, or backup iron sights.
- Stripped Armorer Custom Configuration: Ships completely bare of forward assist and dust cover hardware, giving armorers total freedom to install customized lightweight or duty parts.
- Flawless Lower Receiver Alignment: Machined to clean mil-spec exterior and lug tolerances, guaranteeing a rock-solid, wobble-free pin fit with standard lower receiver frames.
Product Specifications
- Brand: Ruger® / Sturm, Ruger & Co., Inc. (Mayodan, North Carolina / Southport, Connecticut)
- Model Line: Factory Original Equipment (OEM) AR-15 Receiver Build Components
- MPN/SKU Code: 91004 (Stripped AR Upper Specification Base SKU)
- UPC Code Profile: 736676910045
- Firearm Platform Compatibility: Standard AR-15 / M4 Layout Lower Receiver Blocks Natively
- Receiver Style Class: Flat-Top Picatinny Rail Upper with Forward Assist & Dust Cover Provision Cutouts
- Structural Material Base: Die-Forged 7075-T6 Structural Grade Aircraft Aluminum Alloy
- Exterior Surface Protection: Mil-Spec Type III Class 2 Matte Black Hard-Coat Anodized Surface Coating
- Barrel Extension Interface: Precision-Milled M4 Feed Ramp Geometry Contours Natively
- Thread Pitch Standard: 1-1/4\"-18 TPI Standard AR-15 Barrel Nut Thread Configuration
- Takedown Pin Hole Diameter: Standard Mil-Spec 0.250-Inch Pivot and Takedown Pin Alignment Loops
- Full Kit Component Checklist: 1x Rugged Bare Forged Stripped Upper Receiver Shell Component Only
- Packaging Format Class: Factory Original Sealed Ruger Branded Box Pack with Internal Inventory Asset Tags
- Product Type Category: Rifle Components / Stripped Upper Receivers & Custom Builder Blanks
- Overall Mechanical Unit Width: ~2.00 Inches (~50.8 mm Standard Extractor Clearance Width Metrics)
- Overall Physical Unit Length: ~7.65 Inches (~194.3 mm Linear Outer Receiver Profile Frame)
- Net Component Module Mass: ~6.90 Ounces (~195.6 Grams Lightweight Structural Forged Weight)
- Global Quality Certifications: Engineered to Professional Duty and Military Dimensional Specifications
- Warranty Tracking Protection: Fully Backed by Ruger Factory Original Product Materials Guarantee
