Aero Precision M4E1 Threaded .300 Blackout Complete Upper Receiver, 8In, 1-7 Twist, 5/8X24 Thread, ATLAS R-ONE Handguard, FDE Cerakote, APAR700711M1

Moriarti Complete Upper Receiver, AR-15, .300 AAC Blackout, 16 Inch Barrel, Medium Profile, Pistol Length, 1X7 Twist, 5/8X24 Thread, M-LOK Handguard, Triport, Hardcoat Anodized, Black, MAR-300-16-15-TRI

Ghost Firearms Elite Complete Upper Receiver, .300 Blackout, 7.5In, Pistol Length, 4150 Light HBAR Barrel, 1-8 Twist, 7in M-LOK Free Float Hand Guard, A2 Flash Hider, Flat Dark Earth, GF75E7GFR300FDE

Aero Precision M4E1 Threaded .300 Blackout Complete Upper Receiver, 10In, 1-7 Twist, 5/8X24 Thread, ATLAS R-ONE Handguard, Black Anodized, APAR700702M4

Tacfire Complete M-LOK Upper Assembly, .300 Blackout , 8In, Type III Hard Anodized, Black, Large, BU-300-8

LANTAC 16in Recon Complete Upper Receiver, 300 Blackout, 5/8-24 UNF, Pistol Length, Black, 01-FA-300-RECON-UPR

Radian Weapons Model 1 Complete Upper Receiver, .300 AAC Blackout, 9 in Barrel, Custom, Pistol Length, 1-5 Twist, 5/8X24 Thread, M-LOK, Deadair Flash Hider, Radian Black, R0027

Grid Defense Complete Upper Receiver, .300 Blackout, 7.5 Inch, Pistol Length, 4150 Light HBAR Barrel, 1-8 Twist, 9 Inch Octagon M-LOK Hand Guard, Dimpled Flash Can, Tactical Grape, GD75GDR9FCAN300GRP

Blackout Defense Complete Dual Taper Lock .300 AAC Upper Receiver Group, Slick Side, 13.9in Pistol, FDE, URGDTL300BLK13.9SLKFDE

Blackout Defense Complete Dual Taper Lock .300 AAC Upper Receiver Group, Forward Assist, 14.5in Pistol, Burnt Bronze, URG-DTL-300BLK-14.5-FWD-BB

Lantac USA LLC Urban Tactical, Complete Upper Receiver, 300 Blackout, 11.5 Barrel, Fits AR-15, Anodized Finish, Black 01-FA-300-UTP-UPR

XTS Complete Upper Receiver W/O BCG, AR-15, 300 BO, 24.75In, 16in Barrel, Carbine, 1-8 Twist, 5/8X24 Thread, M-LOK, Bird Cage, Black Nitride Finish, XTSCU16300BK

XTS Complete Upper Receiver W/O BCG W/ 12in Rail, AR-15, 300 BO, 24.75In, 16in Barrel, Carbine, 1-8 Twist, 5/8X24 Thread, M-LOK, Bird Cage, Black Nitride Finish, XTSCU12300BK

Ghost Firearms Upper Receiver, Pistol Lower Parts Kit, .300 Blackout, 7.5In, Pistol , 4150 Light HBAR Barrel, 1-8 Twist, 9in M-LOK Free Float Hand Guard, Flash Can, FDE, GF75GFR9FCAN300FDE-KIT

XTS Complete Upper Receiver W/O BCG, AR-15, 300 BO, 19.5In, 10.5In, Pistol, 1-8 Twist, 5/8X24 Thread, M-LOK, Bird Cage, Black Nitride Finish, OD Green, XTSCUBO10OD

Blackout Defense Complete Dual Taper Lock .223 Wylde Upper Receiver Group, Forward Assist, 11.5in Carbine, Grey, URG-DTL-223W-11.5-FWD-GRY