GMI Upper Build Kit

MSRP: $275.00
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This is a partially assembled upper kit without a handguard.

The upper receiver small parts (forward assist and dust cover) are installed. The gas tube is installed in the gas block. The gas block and muzzle device are NOT installed on the barrel.

As such, this product is only warrantied for defects in our installation or manufacturing.


All Grey Mesa Industries components are 100% made in the USA - no Chinese small parts.


Accuracy Guarantee: 1" @ 100yds

Barrel: 16” Ballistic Advantage Pencil Profile, Mid-length

Barrel Extension: M4 with QPQ Finish

Gas Block Type: 0.625” nitrided steel low profile

Muzzle Device: A2 Flash Hider

Upper Receiver Type: M4 (with feed ramps)

Bolt Carrier Group: PSA Milspec with HPT/MPI C158 Bolt, Anderson Phosphate Finish and Chrome Lined with 9310 Bolt, or none

Charging Handle: GMI 7075 T6 Forged Mil-spec, GMI 6061 Forged, or none


In order to complete the upper:

1. Acquire a handguard

2. Install gas block by applying loctite and tightening set screws

3. Install handguard

4. Install flash hider

5. If you didn't buy them from us, acquire BCG and charging handle

6. Install BCG and charging handle