What is the SA-4 16" Mid-length M-LOK?
The SA-4 is a complete, ready-to-shoot AR-15 rifle chambered in 5.56 NATO, featuring a 16" mid-length barrel configuration. Built with forged 7075-T6 aluminum receivers, a 4150 CMV nitride-finished barrel, and Shield Arms' adjustable gas block, this rifle delivers reliable performance at a lightweight 6.7 pounds. It's designed as a no-nonsense, dependable weapon system that includes everything you need without unnecessary features or weight.
Complete Package Includes:
- Fully assembled rifle with B5 Systems Bravo stock
- Two magazines included
- Ready to shoot out of the box
Enhance Your Setup:
Purpose-Built Reliability in a Lightweight Package
The SA-4 16" Mid-length M-LOK represents Shield Arms' philosophy of purposeful design: everything you need and nothing you don't. This complete AR-15 rifle is built on time-tested forged 7075-T6 aluminum receivers that provide exceptional strength and durability at a lower weight compared to billet alternatives. The 16" barrel features a mid-length gas system—widely regarded as the optimal gas system length for 16" barrels—delivering smoother recoil impulse, reduced wear on components, and improved reliability compared to carbine-length systems. The 4150 chrome-moly-vanadium steel barrel is stress-relieved after rifling and finished with black nitride for exceptional corrosion resistance and bore longevity.
At the heart of this rifle's reliability is Shield Arms' adjustable gas block, which allows you to fine-tune gas flow for different ammunition types, suppressors, or environmental conditions. The 13" M-LOK handguard provides ample mounting space for accessories while maintaining a slim profile that's comfortable for various hand sizes and shooting styles. The handguard's length allows for a modern support-hand grip position while protecting your hands from the mid-length gas system's port location. Combined with the B5 Systems Bravo buttstock, mil-spec components throughout, and a complete bolt carrier group that's been shot-peened and magnetic particle inspected, the SA-4 delivers professional-grade reliability.
Weighing just 6.7 pounds, the SA-4 strikes an ideal balance between lightweight maneuverability and stability during extended shooting sessions. The 1:7 right-hand twist rate stabilizes a wide range of bullet weights from 55-grain to 77-grain, making this rifle versatile for everything from plinking and training to home defense and competitive shooting. Every SA-4 is assembled to exacting standards in the USA and backed by Shield Arms' 100% lifetime warranty, ensuring you have a reliable partner for years to come.
Key Features
- 16" 4150 CMV Barrel: Chrome-moly-vanadium steel construction with black nitride finish, stress-relieved after rifling for accuracy and longevity
- Mid-Length Gas System: Optimal gas system length for 16" barrels provides smoother shooting, reduced recoil, and enhanced reliability
- Shield Arms Adjustable Gas Block: Tune gas flow for different ammunition, suppressors, or operating conditions for maximum versatility
- Forged 7075-T6 Receivers: Military-grade forged aluminum upper and lower receivers deliver proven strength and durability
- 13" M-LOK Handguard: Free-floating design with M-LOK mounting system provides secure accessory attachment and improved accuracy
- Premium Bolt Carrier Group: Shot-peened, magnetic particle inspected BCG with 9310 steel bolt and 8620 M16 carrier, black nitride finished
- 1:7 Twist Rate: Stabilizes bullet weights from 55 to 77 grains for ammunition versatility
- B5 Systems Bravo Stock: Durable, lightweight carbine stock with secure locking mechanism
- Lightweight Design: Just 6.7 pounds complete, ideal for extended carry and rapid handling
- 5.56 NATO Chamber: Safely fires both 5.56 NATO and .223 Remington ammunition
Understanding the Mid-Length Advantage
Why Mid-Length Gas Systems Matter:
The mid-length gas system on the SA-4's 16" barrel positions the gas port approximately 9 inches from the chamber, compared to 7 inches for carbine-length systems. This additional dwell time results in lower bolt velocity, reduced felt recoil, decreased wear on components, and improved reliability. The mid-length system also produces less gas blowback to the shooter's face, especially important when running a suppressor. For a 16" barrel, mid-length is the gold standard for balanced performance.
Technical Specifications
| Caliber/Chamber |
5.56 NATO (also fires .223 Remington) |
| Barrel Length |
16 inches |
| Barrel Material |
4150 Chrome-Moly-Vanadium Steel |
| Barrel Finish |
Black Nitride |
| Twist Rate |
1:7 Right-Hand |
| Gas System |
Mid-Length |
| Gas Port Diameter |
.076 inches |
| Gas Block |
Shield Arms Adjustable Gas Block |
| Upper Receiver |
7075-T6 Forged Aluminum |
| Lower Receiver |
7075-T6 Forged Aluminum |
| Handguard |
Shield Arms 13" M-LOK Free-Float |
| Bolt Material |
9310 Steel |
| Carrier Material |
8620 Steel (M16 Profile) |
| BCG Finish |
Black Nitride |
| Trigger |
Enhanced Mil-Spec |
| Safety Selector |
Mil-Spec |
| Buttstock |
B5 Systems Bravo |
| Grip |
Mil-Spec A2 |
| Trigger Guard |
B5 Systems |
| Charging Handle |
Mil-Spec |
| Muzzle Device |
A2 Flash Hider |
| Weight |
6.7 lbs |
| Included |
Two Magazines |
| Manufacturing |
Made in USA |
| Warranty |
Lifetime Warranty |
Mid-Length vs. Carbine-Length Gas Systems
| Feature |
SA-4 Mid-Length (16") |
Carbine-Length (16") |
| Gas Port Location |
~9 inches from chamber |
~7 inches from chamber |
| Dwell Time |
Optimized for 16" barrel |
Over-gassed on 16" barrel |
| Recoil Impulse |
Smoother, more controllable |
Sharper recoil impulse |
| Component Wear |
Reduced wear on BCG and buffer |
Increased wear from excess gas |
| Reliability |
Excellent with various ammo |
May require tuning |
| Suppressor Ready |
Less gas blowback |
More gas blowback to face |
Frequently Asked Questions
What ammunition can I shoot in the SA-4?
The SA-4 is chambered in 5.56 NATO and can safely fire both 5.56 NATO and .223 Remington ammunition. The 1:7 twist rate stabilizes bullet weights ranging from 55 grains up to 77 grains, making it compatible with most common AR-15 ammunition on the market.
Is the SA-4 suitable for home defense?
Yes. The SA-4's 16" barrel provides excellent velocity for defensive ammunition while remaining maneuverable indoors. The mid-length gas system offers smoother recoil for faster follow-up shots, and the adjustable gas block ensures reliable cycling with various ammunition types. At 6.7 pounds, it's light enough for extended holding positions yet substantial enough to manage recoil effectively.
Can I add a suppressor to the SA-4?
Absolutely. The SA-4's adjustable gas block makes it particularly well-suited for suppressor use. When adding a suppressor, you can reduce gas flow to minimize blowback and maintain optimal cycling. Simply remove the A2 flash hider and install your suppressor per the manufacturer's instructions. The mid-length gas system produces less gas blowback than carbine-length systems when suppressed.
How do I adjust the gas block on the SA-4?
The Shield Arms adjustable gas block features a set screw that controls gas flow. To adjust, ensure the rifle is unloaded, access the gas block adjustment screw (typically from the side or underside), and turn it to increase or decrease gas flow. Start with the gas block fully open, then gradually restrict gas until the rifle reliably locks back on the last round. For detailed instructions, visit our installation guides.
What is the effective range of the SA-4?
With the 16" barrel and 1:7 twist rate, the SA-4 is effective out to 500-600 yards in the hands of a skilled shooter, though practical accuracy for most shooters will be excellent to 300-400 yards. The mid-length gas system and free-floating handguard contribute to consistent accuracy, while the barrel's stress-relieved construction ensures precision shot placement.
Can I mount accessories to the M-LOK handguard?
Yes. The 13" M-LOK handguard accepts all M-LOK compatible accessories including lights, lasers, foregrips, and sling mounts. M-LOK provides a slim profile when accessories aren't attached, while offering secure, repeatable mounting when they are. The handguard's length provides ample real estate for multiple accessories without adding unnecessary weight.
Is the SA-4 legal in all states?
The SA-4 features a standard 16" barrel and traditional configuration that complies with federal law. However, state and local laws vary significantly. Some states have restrictions on semi-automatic rifles, magazine capacity, or specific features. It is the purchaser's responsibility to ensure compliance with all applicable federal, state, and local laws before purchasing. The SA-4 must be transferred through a licensed FFL dealer.
What makes the BCG in the SA-4 special?
The SA-4's bolt carrier group undergoes shot peening and magnetic particle inspection—processes typically reserved for higher-end rifles. Shot peening improves fatigue resistance and longevity, while magnetic particle inspection detects microscopic cracks or defects. The 9310 steel bolt is stronger than standard Carpenter 158 steel, and the black nitride finish provides superior corrosion resistance compared to phosphate coatings.
Can I upgrade components on the SA-4?
Absolutely. The SA-4 uses mil-spec components throughout, making it compatible with the vast majority of AR-15 aftermarket parts. Common upgrades include triggers, charging handles, pistol grips, stocks, and muzzle devices. The forged receivers accept any mil-spec upper or lower components, giving you complete flexibility to customize the rifle to your preferences.
What warranty does the SA-4 include?
Every SA-4 rifle is backed by Shield Arms' 100% lifetime warranty covering defects in materials and workmanship. This warranty covers the complete rifle for as long as you own it, demonstrating Shield Arms' commitment to quality and customer satisfaction.
How accurate is the SA-4?
The SA-4 is designed to deliver 2-3 MOA accuracy with quality ammunition, which is excellent for a general-purpose rifle. The free-floating M-LOK handguard eliminates barrel contact that can affect accuracy, while the stress-relieved barrel and quality chamber ensure consistent performance. Accuracy is sufficient for all practical applications including home defense, hunting, and competitive shooting.
Does the SA-4 come with iron sights?
The SA-4 as shipped does not include iron sights, allowing you to choose your preferred sighting system. The flat-top upper receiver accepts any Picatinny-mounted optic, red dot, or backup iron sights. This gives you complete flexibility to configure the rifle for your specific use case, whether that's red dot for close range, magnified optic for distance, or co-witnessed irons with a red dot.
Who Should Buy the SA-4 16" Mid-length M-LOK
- First-Time AR-15 Owners: Shooters looking for a complete, reliable rifle without the complexity of building from parts or the guesswork of component selection
- Home Defense Users: Individuals seeking a dependable, maneuverable defensive rifle with the power and capacity advantages of the AR-15 platform
- Practical Shooters and Competitors: 3-gun, multi-gun, and tactical competition shooters who need a lightweight, reliable rifle with mounting options for accessories
- Hunting and Predator Control: Hunters pursuing varmints, predators, or medium game within appropriate ranges who value the AR-15's modularity and magazine capacity
- Training and Range Use: Shooters building skills with a quality platform that's comfortable to shoot for extended periods and compatible with various training accessories
- Suppressor Users: Shooters planning to run a suppressor who need the adjustable gas system
