Description
The Sport line has been the default first AR for over a decade because these rifles just plain run, and the Sport III is the best version of that formula yet. Smith & Wesson took the two things owners used to swap out first, the drop-in handguard and the carbine gas system, and replaced them from the factory. You get a slim 15-inch free-float M-LOK handguard with a full-length Picatinny rail up top, plus a mid-length gas system that softens the recoil impulse and keeps the gun cycling smooth.
What Makes the Sport III Worth a Look
The 16-inch barrel is 4140 chrome moly with an Armornite finish inside and out, cut with 5R rifling in a 1:8 twist. That twist rate matters more than people think. It stabilizes everything from cheap 55 grain plinking ammo up to heavier 77 grain match loads, so you're not locked into one bullet weight. The muzzle is threaded and wears an A2-style device, and the six-position collapsible stock adjusts to fit shooters of different sizes or layers of clothing. At around 6.5 pounds, it carries and handles the way an AR should.
How This M&P15 Sport III Feeds
Model 13955 is the 10-round configuration, and it uses the Juggernaut Tactical magazine lock system paired with a quick-release rear takedown pin. Pop the pin, the action tilts open, and you swap the included 10-round Magpul PMag. It takes a little practice, but the setup becomes second nature fast.
Setting Up Your Sport III
The rifle ships without sights, which is the right call these days since most buyers head straight for a red dot or LPVO anyway. The flat-top upper gives you a clean slate, and all that M-LOK real estate leaves room for a light, sling mount, and hand stop without crowding anything. It's a dependable 5.56 that's ready for range days, training classes, and home defense duty right out of the box.
Key Specifications
- Manufacturer: Smith & Wesson
- Model: M&P15 Sport III
- Manufacturer Part Number: 13955
- UPC: 022188896763
- Caliber: 5.56 NATO / .223 Rem
- Action: Semi-Auto, Gas Operated
- Capacity: 10+1
- Barrel Length: 16 in
- Barrel: 4140 Chrome Moly, Armornite Finish, Threaded
- Rifling: 1:8 Twist, 5R
- Gas System: Mid-Length
- Handguard: 15 in Free-Float M-LOK
- Stock: 6-Position Collapsible
- Magazine System: Juggernaut Tactical Mag Lock w/ Quick-Release Rear Takedown Pin
- Sights: None, Optics-Ready Flat Top
- Weight: 6.5 lbs
What’s Included
- M&P15 Sport III rifle
- One 10-round Magpul PMag
- Owner's manual
- Cable lock
Frequently Asked Questions
Does the M&P15 Sport III 13955 come with sights?
No, this model ships without sights. The flat-top upper has a full-length Picatinny rail, so you can mount a red dot, LPVO, or a set of backup irons however you like. Most buyers plan on adding an optic anyway, so you're not paying for irons you'd remove.
What's different about the Sport III compared to the Sport II?
The Sport III adds a 15-inch free-float M-LOK handguard in place of the old drop-in plastic guard, switches to a smoother mid-length gas system, and upgrades to a 1:8 twist barrel with 5R rifling. Those were the three most common upgrades people made to the Sport II, and now they come standard from the factory.
How does the magazine system work on this version of the Sport III?
Model 13955 uses the Juggernaut Tactical magazine lock system with a quick-release rear takedown pin. To reload, you release the pin, the action opens, and you swap the 10-round magazine. It's a different rhythm than a standard mag release, but it becomes quick with a little practice.
What ammo runs best in the M&P15 Sport III?
It's chambered for 5.56 NATO, so it safely handles both 5.56 and .223 Remington. The 1:8 twist barrel stabilizes a wide range of bullet weights, from 55 grain range ammo up to 77 grain match loads. For casual range work, standard 55 grain FMJ is affordable and runs great.





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