.300 Blackout AR-15 Pistol Kit (8.5” Barrel & 9” Lightweight MLOK Handguard) with 80% Lower (1:8 Twist)



Wanna squeeze more performance out of your .300 AAC blackout AR when it comes to subsonic rounds?  If you plan to get a suppressor, then you need this AR build kit chambered in .300 BLK! Its shorter barrel when paired with a suppressor makes an excellent means of slingin’ lead downrange.

This build kit starts with an upper assembly made of an 8.5 inch barrel with a 9 inch lightweight M-Lok handguard.  You also get a lower parts kit that comes with a polished trigger for a little smoother performance, a Magpul MOE grip, and the SBA3 adjustable pistol brace by SB Tactical.  Last but not least, the backbone of the entire build kit: your choice of one of our 7075 T6 forged aluminum or 6061 T6 billet aluminum 80% lowers. Alternatively, you can choose to go with no lower at all if you’ve already got it worked out.  Happy building!

AR-15 Pistol Build Kit Specs:

Barrel Length: 8.5″

Barrel Steel: Chrome Moly Vanadium

Barrel Finish: Phosphate

Muzzle Thread: 5/8 x 24

Chamber: .300 AAC Blackout

Twist Rate: 1:8

Muzzle Device: Fluted Flash Can

Receiver Material: 7075 T6 Forged Aluminum

Receiver Type: M4

Handguard Type: 9” Lightweight M-Lok

Bolt Carrier Group Included: Yes

Bolt Steel: Carpenter 158

Charging Handle Included: Yes

AR-15 Pistol Build Kit Features:

  • Complete build kit w/ optional lower
  • Includes pre-built .300BLK AR upper
  • High-quality CMV barrel for accuracy
  • Features enhanced, polished trigger
  • Not considered a firearm, no FFL required
  • Proudly built in the U.S.A.
  • Backed by Lifetime Warranty

Barrel: Phosphate-coated, 8.5”, chambered in .300BLK. Made of 4150 CMV steel. Heat-treated. Features 1:8 twist rate. Includes 9” M-Lok handguard, and fluted flash can.

Upper: Made of 7075 T6 forged aluminum. Hard-coat anodized (Type III).

Bolt: Heat-treated. Nitride finish. Carpenter 158 steel.  Full auto profile.

80% Lower: Complete with optional AR-15 80% lower. Mil-spec fittings. Type III Hardcoat anodized finish.

Lower Parts Kit: Mil-spec AR-15 lower parts kit. Enhanced, polished trigger (EPT). Six-position buffer tube. SB Tactical Pistol Brace. Magpul MOE grip. Carbine buffer spring and pistol buffer.

Charging Handle: Standard AR-15 charging handle.

Please note: If completing your AR-15 build using the optional 80% lower, please select an AR-15-compatible 80% jig from the available options on our website.

No FFL required  Made in the USA  Lifetime Warranty

Shipping Restrictions

Shipping of various parts and/or accessories are prohibited to states and locales (ie New Jersey, California, New York, etc…) with restrictions against certain parts and/or accessories or “assault weapons” (i.e. states with high-capacity magazine restrictions, manufacturing of semi-automatic weapons, etc..). It is your responsibility to be aware of your local firearms laws before purchasing from our website or machining a firearm. We try our best to keep our shipping page current, but laws change daily

80-Lower.com only ships within the United States. Federal legislation dictates we cannot ship our products internationally.