What is the SA-15 Complete Folding Lower Receiver?
The SA-15 Complete Folding Lower Receiver is a premium, fully-assembled AR-15 lower receiver featuring Shield Arms' patented built-in folding mechanism. Unlike adapter-based folding systems, this innovative design integrates the folding capability directly into the receiver, eliminating 0.5+ pounds of unnecessary weight while providing compact storage and transport.
Perfect For:
- Shooters seeking maximum portability without weight penalty
- Vehicle and backpack carry applications
- Complete builds requiring premium components
- Pair with: Mountain Partisan Sling for optimal carry configuration
Premium Complete Lower with Integrated Folding Technology
The SA-15 Complete Folding Lower Receiver represents a significant advancement in AR-15 design, combining Shield Arms' patented folding mechanism with premium components from industry-leading manufacturers. Machined from 7075-T6 aircraft-grade billet aluminum and finished with mil-spec hard-coat anodizing, this complete lower delivers exceptional durability and reliability. The built-in folding mechanism is not an aftermarket adapter—it's engineered directly into the receiver design, resulting in a cleaner appearance, reduced weight, and improved structural integrity compared to conventional folding adapters.
This complete lower arrives ready to mate with your upper receiver, featuring carefully selected components that enhance performance and usability. The B5 Systems Bravo buttstock provides robust, comfortable shouldering, while the ALG Advanced Combat Trigger delivers crisp, consistent trigger control. The Radian Safety Selector offers ambidextrous operation, and the B5 Systems grip ensures secure handling in all conditions. Every component is assembled to exacting standards and backed by Shield Arms' 100% lifetime warranty.
Designed for shooters who demand the ultimate in portability without compromising on quality, the SA-15 accepts all standard AR-15 magazines and is compatible with most aftermarket parts. The precision-machined magazine well features a beveled feed lip for rapid reloads, while thoughtful engineering touches like the threaded takedown pin hole and upper tension screw allow for perfect customization of fit and function. At just 2.45 pounds, this complete lower provides a lightweight foundation for any build while maintaining the strength and durability required for serious use.
Key Features
- Patented Built-In Folding Mechanism: Integrated design eliminates the need for external adapters, saving 0.5+ pounds compared to popular folding adapter systems
- Premium 7075-T6 Billet Aluminum: Aircraft-grade material machined to tight tolerances for superior strength-to-weight ratio
- Mil-Spec Hard-Coat Anodized Finish: Matte black Type 3 Class 2 anodizing per Mil-8625 specification provides exceptional corrosion and wear resistance
- B5 Systems Bravo Buttstock: Durable, lightweight carbine stock with secure locking mechanism and storage compartment
- ALG Advanced Combat Trigger: Crisp, clean trigger pull
- Radian Ambidextrous Safety Selector: Precision-machined safety for both left and right-handed shooters
- Proprietary H2 Buffer: Optimized buffer weight included for reliable cycling across a wide range of configurations
- Enhanced Fitment Features: Threaded takedown pin hole with 6-32 set screw, upper tension screw, and threaded bolt catch pin for perfect fit
- Universal Compatibility: Accepts standard AR-15 magazines and works with most standard and aftermarket AR-15 components
- Precision Magazine Well: Beveled feed lip design facilitates fast, fumble-free magazine changes
Important Notes
Complete Lower Assembly: This is a fully assembled lower receiver. No additional lower parts kit required.
Assembly Requirements: Requires an AR-15 upper receiver assembly to complete your firearm. Buffer system and stock are pre-installed.
Caliber Marking: Marked "MULTI" to accommodate various caliber configurations when paired with appropriate upper receivers and barrels.
Legal Compliance: As a complete lower receiver, this product is regulated as a firearm and must be transferred through a licensed FFL dealer. Ensure compliance with all federal, state, and local laws before purchase.
Technical Specifications
| Material |
7075-T6 Aircraft Grade Billet Aluminum |
| Finish |
Matte Black Hard-Coat Anodized (Mil-8625 Type 3 Class 2) |
| Weight |
2.45 lbs (complete assembly) |
| Buttstock |
B5 Systems Bravo Carbine Stock |
| Trigger |
ALG Advanced Combat Trigger |
| Safety Selector |
Radian Ambidextrous Safety Selector |
| Grip |
B5 Systems Grip |
| Buffer |
Shield Arms Proprietary H2 Weight Buffer (included) |
| Magazine Compatibility |
All Standard AR-15 Magazines |
| Caliber Marking |
MULTI |
| Manufacturing |
Made in USA |
| Warranty |
Lifetime Warranty |
Built-In vs. Adapter-Based Folding: The Advantage
| Feature |
SA-15 Built-In Folding |
Typical Folding Adapter |
| Weight |
2.45 lbs complete |
0.5+ lbs heavier due to adapter |
| Design Integration |
Patented built-in mechanism |
External adapter attachment |
| Profile |
Sleek, integrated appearance |
Bulkier with visible adapter |
| Structural Integrity |
Single-piece design |
Additional connection point |
| Installation |
Ready to use out of box |
Requires installation and timing |
| Components Included |
Complete with premium parts |
Adapter only, parts sold separately |
Frequently Asked Questions
Can I fire the rifle when the lower is in the folded position?
No. The SA-15 Folding Lower Receiver should only be fired when fully extended and locked in the open position. The folding feature is designed for storage and transportation, not for firing in the folded configuration.
Is the SA-15 compatible with my existing AR-15 upper receiver?
Yes. The SA-15 features standard AR-15 upper receiver interface dimensions and is compatible with most mil-spec and commercial upper receivers. The included upper tension screw allows you to eliminate any play between upper and lower receivers for a tight, rattle-free fit.
What magazines work with the SA-15 Folding Lower?
The SA-15 accepts all standard AR-15 magazines, including PMAG, USGI aluminum magazines, and other aftermarket options. The precision-machined magazine well with beveled feed lip ensures smooth insertion and reliable feeding.
How much weight does the built-in folding mechanism save compared to folding adapters?
The SA-15's integrated folding design saves 0.5 pounds or more compared to popular folding adapter systems. This is achieved by engineering the folding capability directly into the receiver, eliminating the need for heavy external adapters while maintaining structural strength.
Does the SA-15 come with a buffer and spring?
Yes. The SA-15 Complete Folding Lower Receiver includes a proprietary H2 weight buffer specifically designed for optimal performance with the folding mechanism. The buffer tube, spring, and all necessary components are pre-installed and ready to use.
Can I replace the stock and grip with aftermarket options?
Absolutely. While the SA-15 comes with premium B5 Systems components, the mil-spec buffer tube accepts any carbine-length AR-15 stock, and the grip can be swapped for any AR-15 compatible pistol grip. The quality components included are selected for reliability, but customization is fully supported.
Is this lower receiver legal in all states?
Firearm laws vary significantly by state and locality. The SA-15 is a complete lower receiver and is regulated as a firearm requiring transfer through an FFL dealer. Some states have specific restrictions on folding stocks or AR-15 configurations. It is the purchaser's responsibility to ensure compliance with all applicable federal, state, and local laws before purchasing.
What is the caliber marking on the SA-15?
The SA-15 is marked "MULTI" to provide flexibility for various caliber builds. When paired with the appropriate upper receiver, barrel, and bolt carrier group, this lower can accommodate multiple calibers including 5.56 NATO/.223 Remington, 300 Blackout, and other AR-15 compatible chamberings.
How do I adjust the upper to lower receiver fit?
The SA-15 includes a threaded upper tension screw located behind the grip screw. By adjusting this set screw, you can eliminate any vertical play between your upper and lower receivers, ensuring a tight, precision fit. Hardware is included, and adjustment is simple with a hex wrench.
What warranty coverage does the SA-15 include?
The SA-15 Complete Folding Lower Receiver is backed by Shield Arms' 100% lifetime warranty. This covers defects in materials and workmanship for the life of the product. Shield Arms stands behind every product manufactured in their facility.
Can I install a different trigger in the SA-15?
Yes. While the SA-15 comes with the excellent ALG Advanced Combat Trigger, the lower receiver accepts any mil-spec or drop-in AR-15 trigger assembly. The trigger pins are standard diameter, making trigger upgrades or replacements straightforward.
How compact is the rifle when folded?
The folding mechanism significantly reduces the overall length of your rifle for storage and transport. The exact folded length depends on your upper receiver and barrel configuration, but the SA-15's folding design provides maximum compactness for vehicle storage, backpack carry, and discreet transportation while maintaining quick deployment capability.
Who Should Buy the SA-15 Complete Folding Lower
- Vehicle Operators and Mobile Shooters: Law enforcement, security professionals, and vehicle-based shooters who need compact storage without sacrificing capability
- Backpack and Pack Rifle Builders: Hunters, hikers, and outdoor enthusiasts building ultra-portable AR-15 configurations for backcountry travel
- Space-Conscious Gun Owners: Anyone with limited storage space who needs maximum compactness for home, vehicle, or safe storage
- Quality-Focused Builders: Shooters who want a complete lower with premium components rather than assembling from individual parts
- Weight-Conscious Shooters: Users building lightweight rifles who want folding capability without the weight penalty of adapter systems
- Professional Users: Military, law enforcement, and security personnel requiring reliable folding capability for specialized applications
- Competition Shooters: 3-gun and multi-gun competitors who transport rifles frequently and value compact storage between stages
Made in USA with Lifetime Warranty
Every SA-15 Complete Folding Lower Receiver is proudly manufactured in the United States using American materials and craftsmanship. Shield Arms' commitment to quality is backed by a 100% lifetime warranty covering defects in materials and workmanship. When you choose Shield Arms, you're investing in American manufacturing excellence and support that lasts a lifetime.
Related Products & Accessories
- Mountain Partisan Sling: Purpose-designed for tactical and backpack carry applications. The ideal pairing for the SA-15's portability-focused design, providing secure retention and rapid deployment capability.
- AR-15 Upper Receivers: Complete your build with a quality upper receiver assembly. The SA-15's universal compatibility ensures proper fit with most mil-spec and commercial uppers.
- Backup Iron Sights: Essential for any defensive or field rifle build. Co-witness capable sights provide a reliable sighting system regardless of optic configuration.
- Optics and Red Dots: Modern optics enhance the SA-15's capabilities for rapid target acquisition. Choose from red dots for close range or magnified optics for extended distance shooting.
Installation & Assembly
The SA-15 Complete Folding Lower Receiver arrives fully assembled and ready to mate with your AR-15 upper receiver. Simply attach your complete upper, ensure proper headspace with your chosen caliber, and perform a function check. For builders new to AR-15 assembly or those seeking additional guidance on upper installation and function checking, visit our comprehensive installation guides for step-by-step instructions and helpful tips.
