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Questions & Answers
Will this work with a 5.56 lower Expert Answer

Yes, the Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly will be compatible with a standard AR15 lower receiver.

by Ethan, Gear Expert, January 25, 2023
What are the actual weights of these ultralight complete uppers? The details say 7.7 oz., which clearly is incorrect. Expert Answer

The Jacob Grey Custom Ultralight 300 BO Complete Upper Assembly weighs 3lbs 4oz (8"), 3lbs 6oz (10.5"), 3lbs 8oz (13"), and 4lbs 1oz (16").

by Ethan, Gear Expert, September 14, 2022
Customer Reviews
Helpful Positive Review
75% quality by Ben Dandrea, Verified Owner, July 22, 2024
I purchased the 8 inch 300blk upper and probably have 500 rds through it currently. Charging handle wore quickly to bare aluminum and I also had the gas tube misalign with the gas key causing damage, Jacob Grey handled it well though and repaired it ...
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2/2 found this helpful
Helpful Positive Review
blown away by MuGGzy, Verified Owner, November 26, 2024
Never heard of the brand but this upper was less than half what others i was looking at were. Pre matched parts make it pre tuned basically. It also has some sweet weight reducing milling. So far it cycles 300 supers right out of the box on the low...
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1/1 found this helpful
Helpful Positive Review
13in 300BLK Upper by SD, Verified Owner, July 7, 2024
Overall it’s a quality upper that I can accurately put rounds down range with. Plus it sounds so good suppressed.
1/1 found this helpful
Helpful Positive Review
well made over all by Nadeem, Verified Owner, February 5, 2025
The upper was leightweight, well built, charging handle was nice and muzzle flash. Polymer upper. Only draw back was front take down pin hole was very tight. Had to file down a bit. Other than that, very good and smooth.
1/1 found this helpful
Most Recent Reviews
Exudes quality by Nick, member from Fl, Verified Owner, June 23, 2024
The fit and finish of this upper assembly exudes quality from end to end. Have no lower to put it on yet but I have no doubt it’ll perform very well once it’s completed. The quality for the price I paid is well worth it!
0/1 found this helpful
Most Recent Reviews
Jacob grey by Stephen Mcmorris, Verified Owner, December 14, 2023
Super nice upper!!! Light, but very well made!!! Comes with upgraded charging handle…a lot of attention to detail!!!
Read All 6 Reviews

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Product Info for Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly

The Jacob Grey Ultralight Complete Upper Assembly was designed with the next generation AR-15 in mind. This AR-15 complete upper assembly is built around the 7075-T6 billet upper receiver specifically machined and cut in areas where excess material was unnecessary and areas that see excess use and wear, reinforced and strengthened to give a sleek, refined look, without losing the classic lines of the AR-15 platform. It comes standard with the JG designed free float 7-sided M-LOK hand-guard that is also lightweight and leaves plenty of room for customization or the addition of numerous accessories available for the AR-15 platform. The barrel is chambered in 300 Blackout with a 1:8 twist rate. The barrel is machined from 4150 chrome moly steel and black Nitride finished for corrosion resistance and accuracy. Each barrel is individually head-spaced to the Carpenter 158 bolt. Combined with the 8620 steel carrier and black Nitride finish, this complete upper assembly is extremely reliable and smooth shooting.image

DISCLAIMER: Firearm specifications are subject to change at any time based on availability and supply chain shortage.

Specifications for Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly:

Manufacturer: Jacob Grey Firearms
Caliber: .300 AAC Blackout
Barrel Profile: Pistol Caliber Taper, Medium Taper
Gas System Length: Pistol Length
Barrel Twist Rate: 1-8
Threads per Inch: 5/8x24
Handguard Type: Free-Float
Muzzle Device: Brake
Finish: Type III Class 2 Hardcoat Anodized
Color: Black
Fabric/Material: Aerospace Aluminum
Gas Block Journal Size-Diameter: .075 in
Handguard Style: Round Rail
Gun Rail: M-LOK
Gun Type: Rifle
Gun Make: AR Platform
Gun Model: AR-15
Weight: 7.7 oz
Barrel Material: Chrome Moly
Gas Block Journal Size-Length: 1.9 in
Bolt Carrier Group Included: MIL-SPEC
Magazine Included: No
Charging Handle Included: MIL-SPEC
Mount Type: M-LOK

Features of Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly

  • Compatible with most aftermarket/OEM handguards featuring indexing tabs
  • Billet 7075-T6 aerospace aluminum
  • Jacob Grey lightweight design
  • M4 feed ramps
  • Machined T-marks
  • Laser engraved logo
  • MIL-A-8625F Type III Class 2 hardcoat anodized flat black finish
  • Compatible with MIL-SPEC AR upper receiver parts
  • JG ULTRALIGHT Handguard

Package Contents:

  • Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly

Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly Orderable Models

List of Orderable Models

  • Jacob Grey Firearms Ultralight Complete Upper Assembly, .300 AAC Blackout, 16in, Black, 300BO16ULCUA , MPN: 300BO16ULCUA , UPC: 850040696042 , Code: 4M6-URC-GJUN2-300BO16ULCUA
  • DEMO, Jacob Grey Firearms Ultralight Complete Upper Assembly, .300 AAC Blackout, 10.5in, Black, 300BO105ULCUA , MPN: 300BO105ULCUA-DEMO , Code: 4M6-URC-GJUN2-300BO105ULCUA-DEMO
  • Jacob Grey Firearms Ultralight Complete Upper Assembly, .300 AAC Blackout, 13in, Black, 300BO13ULCUA , MPN: 300BO13ULCUA , UPC: 850040696059 , Code: 4M6-URC-GJUN2-300BO13ULCUA

Jacob Grey Firearms Ultralight 300 BO Complete Upper Assembly Unavailable & Discontinued Models

List of Unorderable Models

  • Jacob Grey Firearms Ultralight Complete Upper Assembly, .300 AAC Blackout, 8in, Black, 300BO8ULCUA , MPN: 300BO8ULCUA , UPC: 850040696073 , Code: 4M6-URC-GJUN2-300BO8ULCUA
  • Jacob Grey Firearms Ultralight Complete Upper Assembly, .300 AAC Blackout, 10.5in, Black, 300BO105ULCUA , MPN: 300BO105ULCUA , UPC: 850040696066 , Code: 4M6-URC-GJUN2-300BO105ULCUA
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