Custom 8.5" 300BO Complete Upper - Upper, 8.5" Barrel, Handguard, Gas Block and Tube, Muzzle Brake

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  • 2 Port Outside Thread Muzzle Brake AR-15 223/556 308 9mm 30cal - 2
  • 3 Port Outside Thread Muzzle Brake AR-15 223/556 308 9mm 30cal - 2

8.5" Complete AR15 300 Blackout Upper

Note: This complete upper receiver assembly has a barrel length under 16” and is therefore subject to all NFA rules and regulations. Know your local laws before purchasing.

Note: Your complete upper will be assembled with the custom parts you pick out, so expect some additional handling time to get your custom build assembled before it ships out. Generally they will still ship out within 2 days (often earlier) depending on what time your order is placed.

The Breek Arms complete AR15 300 Blackout 8.5" upper comes jam packed with features that usually cost you a fortune in order to trick out the plain upper you may have purchased before. Our AR15 complete upper uses quality components that come from trusted companies. The upper comes equipped with an 8.5” barrel, and with a black nitride bolt carrier group you can have flawless function when operating. The upper receiver is from Aero Precision paired with a Breek Arms 9” SPTFR Handguard (or handguard of your choice). In the front, the muzzle device gives you a couple options. Keep it open to lessen the recoil, or if you want to tame the sound simply twist on your optionally included Castle Blast Shield. Last but especially not least, the upper can be equipped with our famous WARHAMMER ambidextrous charging handle for easy one handed manipulation. The upper can be placed on any type of mil spec AR-15 lower.




  • Compatible with Mil-Spec AR-15 lowers
  • Full length picatinny top rail

Breek Arms is dedicated to bringing our people new and improved products and solutions at reasonable prices while maintaining a high quality product. This feature rich and affordable AR15 300BO upper is just another way of fulfilling our mission.

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  • 5
    Great Upper

    Posted by Lance Mears on Dec 12th 2019

    This is the best upper I’ve found for the money. High quality aero upper with a great looking handguard. I haven’t had the chance to shoot it yet but I’m betting it runs flawlessly. Do yourself a favor and get this upper, you won’t be disappointed.

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