.300 Blackout Complete AR-15 Upper Receivers
Complete .300 BLK uppers for your AR-15 make swapping out calibers simple. Re-use your 5.56 BCG and mags!
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AT3™
AT3™ FF-ML 10.5 Inch .300 Blackout Pistol Upper for AR-15 – 12″ M-LOK Free...
AT3 10.5" .300 BLK Pistol Upper with SPEAR M-LOK Handguard - Made to Order and Ships in 7 Days AT3 Complete Upper assemblies are Built for Accuracy and Reliability -...8 Options -
AT3™
AT3™ FF-ML 16 Inch .300 BLK Complete AR 15 Upper – .300 AAC Blackout...
The AT3 16" .300 BLK Rifle Upper with SPEAR M-LOK Handguard - Made to Order and Ships in 7 Days AT3 Complete Upper assemblies are Built for Accuracy and Reliability...8 Options -
Radical Firearms 16″ .300 Blackout Complete AR 15 Upper Receiver with M-LOK Handguard
Complete Budget-Friendly Upper Receiver for .300 Blackout AR Builds The Radical Firearms 16" .300 Blackout Complete Upper Receiver is a great way to start your .300 Blackout AR build. It...
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