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Jacob Grey 300 BlackOut Complete Upper Assembly 8″




Caliber: .300 Blackout

Length: 8″

Gas Seat: 0.750″

Gas Placement: Pistol-Length

Twist Rate: 1:7

Material: CMV Alloy

M4 Feed Ramps: Yes

Muzzle Thread Pattern: 5/8″-24

Finish: QPQ Nitride (Barrel only)


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You won’t get any unneeded features with the Jacob Grey 300 blackout barrel. You get a cold hammer-forged barrel with a reliable pistol gas system. This combination means you get what you expect, the best. To make function meet reliability, the Jacob Grey barrel is designed with a little more wall so that heat is more easily dissipated, and barrel whip is kept to a minimum. We went with 4150 Chrome Moly Vanadium blanks for this 300-blackout barrel. Not only is this design easy to clean, but it’s corrosion resistant as well. Jacob Grey stays true to the industry standard when it comes to the gas-block seat and muzzle threads. Our fully assembled upper comes with a 7” hand guard and a JG 3-Stage Muzzle Brake to help with the muzzle flash from the 30 caliber round that is the 300 Blackout.

Additional Features:

Jacob Grey Ambidextrous Charging Handle

Jacob Grey 7” Hand Guard

JG 3-Stage Muzzle Brake

JG 300 AAC/5.56/.223 Rem Nitride BCG

JG Billet Dust Cover

Class III Type 2 Hard coat anodized finish

Pistol length gas tube

Low profile JG Gas block



While the 300 Blackout round is one of the most popular as of late, the ammunition used greatly affects the performance of your Jacob Grey 300 Blackout upper receiver. While we test our upper receivers using 145gr subsonic ammunition, this may not necessarily be the round you prefer to choose. Buffer weight and spring coil tension greatly affects your firearms performance, and the user may need to adjust buffer weight accordingly to suit your choice of round. H2 and H3 Buffers are commonly used with the 300 Blackout. If unsure about your firearms performance seek help from a qualified gunsmith.


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