BG Upper Build Kit 5.5" 9mm Upper Receiver - Black | FLASH CAN | 7" M-LOK | With BCG & CH

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Product Code: UBK-BG559MM7FC-BLK
Quantity in Stock Quantity in Stock: IN STOCK
MSRP: $441.95
Sale Price: Sale Price: $232.95
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BG Upper Build Kit 5.5" 9mm Upper Receiver - Black | FLASH CAN | 7" M-LOK | With BCG & CH

This build kit DOES NOT come assembled. 

This Complete 5.5 inch M-LOK upper receiver build kit comes with a 7 inch free float handguard and includes only the best Mil-Spec components for your AR15 build. The core components of this kit are a barrel that’s machined from chrome moly vanadium 4150 steel, an M4 upper that is machined from 7075 T6 forgings, and our black nitride bolt carrier group that is finished with an incredible polish, making the action smooth and easy to keep clean.

As a “do it yourselfers" or DIY enthusiast, you may prefer an AR-15 build kit over a complete upper. Building an AR-15 from a kit allows for a greater level of customization and personalization of the final product. DIYers can choose from a variety of components, such as barrels, handguards, and triggers, to create a rifle that meets their specific needs and preferences. Additionally, building an AR-15 from a kit can be a rewarding and educational experience, as it allows you to gain a deeper understanding of how their firearm functions and how to properly maintain it. Building an AR-15 from a kit may often be more cost-effective than purchasing a complete upper, as it allows DIYers to select only the components they need, rather than paying for pre-assembled parts they may not want or need.

**Disclaimer** These barrels have no Index pin or dedicated feed ramps

We also carry this Upper Receiver Kit assembled here.

Caliber 9mm
Length 5.5"
Material 4150 Chrome Moly Vanadium
Profile Straight
Finish QPQ Corrosion Resistant
Gas System Length Blowback
Gas Block Journal .N/A
Dimpled? No
Twist Rate 1:10
Muzzle Thread 1/2x36 TPI
Weight 9.6oz
Barrel Extension Integrated
Target Crown 11 Degree

Bolt Carrier Group:

  • Colt & Glock Compatible
  • USA made 8620 Steel Carrier Construction
  • Phosphated or Nitrided Finish
  • Heavy Firing Pin Retaining Spring
  • 13.7 oz.

Upper Receiver:

  • This .22LR / 9mm upper receiver assembly is made from forged 7075-T6 aluminum and is Hard Coat Anodized. It meets military specifications and comes in a true slick side configuration. The ejection port door is sized for 9mm and 22LR. This upper does not have a forward assist.

    • Machined from a Mil-Spec 7075 T6 forging
    • Type III Hardcoat Anodized finish


  • 7" free float handguard
  • MIL-STD 1913 Picatinny rail on top
  • 2 M-Lok slots on 3 sides
  • Precision Machined 6000 Series aluminum, for high strength and weight savings
  • Hard Coat Anodized per Mil-A-8625F, Type III, Class 2
  • Clamp on system for easy assembly
  • Steel Barrel nut to resist movement under heat
  • 8.9 oz with barrel nut and hardware
  • 1.35" Inside Diameter
  • 1.63" Wide
  • Made in USA

Charging Handle:

  • Alloy Charging Handle Assembly
  • Complete with Standard Latch
  • Made from hardcoat anodized aluminum
  • Black finish