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AR-15 Upper Assembly – 16″ / 300 AAC / 1:8 / 12″ Keymod AR-15 Handguard / Rail

Icon - 300AAC Blackout AR CaliberIcon - 1:8 Twist RateIcon - 16 AR Barrel
(15 customer reviews)

Original price was: $429.00.Current price is: $279.00.

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This AR15 upper receiver assembly comes ready to attach to any Mil-Spec lower receiver. It is?built around a 16 inch, 4150 chrome moly barrel that is chambered in 300 Blackout and has a black nitride finish. The upper receiver is a forged M4 flat top upper, allowing you to easily attach rifle scopes and red dot sights to the picatinny rail. This upper features our most popular rail, our seven-sided second generation keymod.


This AR15 upper receiver assembly comes ready to attach to any Mil-Spec lower receiver. It is?built around a 16 inch, 4150 chrome moly barrel that is chambered in 300 Blackout and has a black nitride finish. The upper receiver is a forged M4 flat top upper, allowing you to easily attach rifle scopes and red dot sights to the picatinny rail. This upper features our most popular rail, our seven-sided second generation keymod.

ar15 upper assembly 16 inch 300 aac 12 inch keymod 160730

Outfitted with our most popular 12? Keymod Rail that features strong attachment points for accessories resulting in accessories and optics having an excellent return to zero capability when detached and reattached. The rail also features a full-length picatinny top rail that sits flush with the upper receiver and has anti-rotation tabs to keep it locked in place. This upper assembly comes with a standard A2 flash hider that effectively suppresses muzzle flash and protects the 5/8?24 barrel threads if you are planning on adding a muzzle break in the future.

  • 7075-T6 Aluminum
  • Mil-Spec Anodized Receiver
  • Pistol Length Gas Tube Assembly
  • 16″ 300 AAC Blackout Barrel
  • 4150 Chrome Moly Steel Nitride Coated Barrel
  • Standard Flash Hider
  • Twist Rate: 1:8
  • 12″ Keymod Handguard/Rail
  • *Does Not Include Bolt Carrier Group & Charging Handle*

Product Details: AR-15 Upper Assembly – 16″ / 300 AAC / 1:8 / 12″ Keymod AR-15 Handguard / Rail

➲ M-LOK Handguard

New for 2022, these AR-15 handguards are built to provide rugged, reliable performance. Designed with the advanced shooter in mind, these handguards are light and ergonomic, features that provide faster on-target performance and reduced fatigue. Includes robust steel mounting hardware to ensure an easy installation and a rock solid platform.

➲ Barrel

The barrel is one of the few components that directly affect the accuracy and weight of your build. ?This barrel has a nitride finish for increased strength and durability.?This provides not only an impressive barrel life but ensures excellent accuracy. The barrel threads are carefully threaded to the .308 standard. Optimized for stability with a 1:8 twist rate, this 300 BLK barrel can handle heavier bullets used for subsonic loads with ease.?

➲ Upper Receiver

The foundation of all good ARs is built upon a dependable upper receiver. CBC upper receivers offer best-in-class quality while providing you years of dependable service. Boasting a MIL-SPEC type III hard coat anodized finish and machined from 7075-T6 forged aluminum, this M4 flat-top receiver delivers a lifetime of superior function. You want your AR built upon a solid platform - this receiver gives you the confidence that your AR-15 will function when it counts most.

➲ Pistol Length Gas Tube

An essential component to your AR15 is the gas tube, which keeps your build up and running. This gas pistol-length tube is constructed from corrosion resistant stainless steel ensuring a lifetime of service.

➲ .750 Low Profile Gas Block

The gas block is a critical link in the chain that is too often overlooked. This component ensures that your AR runs reliably. Made from high-quality steel with a smooth phosphate finish, this .750 low-profile gas block is efficiently designed to stay put with the percussion of gunfire. With its low profile this gas block allows it to fit under the most ergonomically designed handguards and rails on the market.

➲ A2 Flash Hider

The muzzle device is designed to perform a specific task, like suppress flash intensity or reduce felt recoil. This A2 Flash Hider is machined from quality steel and finished with an exceptionally corrosion resistant salt bath nitride for a lifetime of service. It provides effective flash suppression that preserves the shooter?s night vision by disrupting the muzzle flash when firing in low light conditions. While its closed bottom with top and side ports offers reduced dust signature when shooting from the prone position while additionally acting as a compensator.

CBC provides a wide selections of AR-15 upper assemblies in a variety of styles and lengths - all partial AR-15 uppers are assembled with everything less the charging handle and bolt carrier group. Our partial upper assemblies offer quality and performance that will satisfy the most demanding shooter. Better yet, all CBC AR-15 uppers are custom built-to-order enabling us to provide you with the best prices you will find anywhere. The quality of our AR-15 uppers are backed by our Lifetime Warranty - if any CBC upper assembly becomes defective, we will repair or replace it at no charge. Get your AR-15 upper assembly at CBC today!

15 reviews for AR-15 Upper Assembly – 16″ / 300 AAC / 1:8 / 12″ Keymod AR-15 Handguard / Rail

  1. Steve Sewell

    Hands down the best deal for a rifle length 300 upper you will find. Ordered mine last Monday, it arrived Saturday morning, I was at the range 2 hours later. This CBC upper is just as solid and well crafted as other uppers I have that cost double or more. If you are in the market for an inexpensive 300 rifle length upper, stop, get your credit card, and buy now. You won’t be disappointed.

    Side note- I never do reviews, I was so impressed with this upper I needed to share.

  2. Keith

    Haven’t gotten to shoot yet so no “five star” rating but I have no complaints on fit and finish. Snapped right in to my Spikes lower. Four stars for now but could go up or down after a trip to the range. Will update if needed.

  3. Nate T.

    I ordered this upper receiver and the bolt/charging handle and was pleasantly surprised that they placed the bolt and charging handle into the upper receiver before they shipped it to me. Everything looks straight and the quality for the priced is excellent. My upper rail and hand guard rail align pretty close so I am happy with the purchase.

  4. Scott

    This is my first AR and first 300BLK. The upper fit my Bushmaster lower pretty well, only a little daylight if I torqued them. Finish looks great and the rail lines up from the receiver to the hand guard.

    It took me a while to decide which scope to run but I ended up with a Nikon P300BLK 2-7×40. 4 shots to sight in at 50 yards, then a couple more at 100 yards and I ended with a 3 shot group that was right at 1″ from 100 yards. Very happy with that. This will be a close range (inside 150 yards) pig and deer gun and a perfect starter for when my kids are old enough to start shooting.

    I’ve lost count of the number of people I’ve told to get this upper. 2 co-workers bought it and are both happy with theirs too.

  5. Tommy Taylor

    Fast friendly service. I had the complete upper in less than seven days. The 300 blackout fit like a glove on the palmeto arms lower. Complete Carolina build. Thanks for the service.

  6. shawn dixon

    I ordered the 16″ blackout with 13″ CBC Gen 2 rail, it arrived withing 10 business days of ordering. Fit an finish is really good; the receiver itself It is indistinguishable from my BCM upper aside from the BCM logo. The handrail is light but very solid; I placed a bipod at the end of the rail and didn’t notice any flexing. I haven’t removed the rail to inspect the barrel nut but everything seems to be aligned and installed correctly. finish on the barrel is even; a little glossier than I expected but my other AR’s are all parkerized, so I’m used to a very flat finish. On the range, it functioned flawlessly with my DD built lower and LMT bolt carrier group. Using Remington 120gr supper sonic ammo I was able to achieve 1.25 MOA groups. This was shooting prone without a good rest so I’d imagine with a better rest and ammo groups will tighten up even further.
    The only complaint I have, and it is a small one, is that I had a bit of buyers remorse when less than a week after ordering they had a sale which dropped the price of this lower $20+ dollars and which offered the same upper with 15″ handrail at the same price. Had I known, I would have waited a few days to order. I sent an Email to CBC asking if they could throw in a couple rail sections or a coupon to off set the difference in price, but never received a reply. With that said, I’m happy with this upper. I’ll definitely be back when I’m ready to build another rifle, and will recommend them to others.

  7. Dennis T

    I just got back from my indoor rang after firing retail and ammo I reloaded using Winchester 768 powder trickled to 15.5 grains and 150 gr. Hornady full metal jacket ammo. The American Eagle and reload ammo preformed indistinguishable and excellent. With a 3X scope shooting benched @ 25 yards the groupings were on top of each other cutting a big dot on the target. I gave it a 5 star because of the price and functionality. The hand guard is excellent and aligned perfectly and the upper is light and solid. I bought this with the BCG and charging handle and the fit is perfect. The black finish doesn’t seem as durable as my Sig .223 ($1,200) or DPMS .308 ($950) but still good. I bought a Anderson Lower ($136) and this upper ($349) with BCG and Charging handle for less than $500 there is no decision for me. The Fit on my Sig M400 lower had ZERO play between the upper and the Anderson had a tiny bit (but less than many AR’s at Cablellas for more than double the price. I bought a receiver wedge from for $3 that sits behind the back take down pin and it had no play after. I have never noticed any accuracy differences in AR’s with a little play between the upper and lower but I am kind of anal so I put dropped the wedge in.
    I have seen similar hand guards for over $170 alone.
    Great Deal and Very good experience with Chris in sales.
    Buy 2 for the apocalypse 🙂 .

  8. Joe Cash

    I purchased this upper a few months ago but only got around to shooting it and his past weekend. My intention was to build an economical hog gun as my youngest son is now using my Weatherby Vanguard 308 on our hunts. The CBC 300 BO upper fit my S&W M&P lower perfectly. I mounted a Minox ZA 2x10x40mm scope in a Primary Arms one piece mount. I wasn’t sure what to expect in terms of accuracy but since all of our hogs have been taken at ranges less than 100 yards, I would have been OK with accuracy in the 1.5-2 MOA, especially at the price-point CBC is selling this upper . For sighting the gun in I was using Remington 120 grain ammo as I intend to use rounds in the 110-125 gr. range for hunting. After zeroing the gun and scope at 100 yards, I was floored by the groups I was shooting. The CBC upper was consistently putting 3 rounds into .5 to point .75 MOA at 100 yards , shooting off a bench. I can’t wait to start working on handloads to see what this upper can really do. If you are considering a 300 BO upper for your 223/5.56 AR, you need to put CBC on your short- list of candidates.
    Joe C., Pennsylvania

  9. Jason w

    Just received my 300 blackout upper today and would have to say I’m impressed with the overall look of this upper. The hand guard is nice and slim, very comfortable in your hand. Everything arrived tight and gas block is aligned. Won’t get a chance to shoot it for a little bit so I can’t say what the accuracy is like. Will update after shooting. I would def buy from them again

  10. Ryan

    I received my upper and immediately I was impressed by the fit and finish. The keymod works perfect with the bcm keymod rails I have. Took it out shooting and it fires true . this is going to be my main deer gun this year and I’m very excited to use it. For the price I plan on ordering a couple more uppers in other calibers. I highly recommend these uppers.

  11. Kevin Crist

    Looks great, shoots great. I love this upper, best of all, assembled by our veterans. A++. It took about 3 weeks to arrive. Well worth the wait!

  12. Scott

    I replaced the upper 556/223 to the 300 Blackout for deer season this year. It is compatible with the Ruger lower. This was the question I had prior to purchasing CBC upper. Hope this helps others.

  13. Bill

    I wanted to take a chance on this caliber to expand on reloading/hunting options and couldn’t pass on the price. It fit perfectly on a PSA lower and cycles cleanly/reliably with various rounds. Fires really tight groupings at the range, zero issues. I will be utilizing CBC on all future builds. Thanks for the great product and pricing!

  14. Marshall boos

    I bought this upper on a Black Friday sale. It was an impulse buy and I kind of regretted spending the money before Christmas. When I got it I brought it to the range and put A 4 power Acog scope on it. And 100 yards within 10 rounds I was hitting all three shots within three quarters of an inch. 120 gr. Remington supers. I have a hard time getting that out of my 556 uppers. Very well Built and looks phenomenal! I will be buying a 556 next.

  15. Nick

    I bought this 16 inch lower and cut the barrel down to 14.5 inches. I secured a silencerco asr brake on the end. There were some minor issues getting the upper to fit my lower, but nothing a little tlc and patience did not resolve. I completed the lower with an aim surplus nickel boron bolt group and headed to the range with a 3-9×40 Burris scope. 19.5grs of w296 and a hornady 110gr vmax resulted in 1 moa. It loves federal 150gr ball, 3 shots touching at 100. Harvester subsonic 220’s grouped 1.25 inches from the bench at 100 yards. Not bad out of a $244 upper. No complaints other than it took longer than advertised to arrive. Overall very happy with the purchase.

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Additional information

Weight 4.1 lbs
Dimensions 27.5 × 4.5 × 4.5 in

Barrel Length