Aero precision should be ashamed of their poor quality control... - Aero Precision M5 20in .308 SS Complete Upper Receiver with Flash Hider w/ ATLAS S-ONE Handguard

I purchased this upper and fired it for the first time recently. After 8 rounds, I experienced significant deviation in accuracy, followed by two failure to extract events. After a total of 12 rounds, I ceased firing.

Back at the shop, here is what I found:

1. The barrel nut had a measured break torque of 10-12 ft lbs (Aero spec calls for 60 ft lbs). Wear was evident on the cerakote’d thread surfaces of the receiver, with no evidence of anti-seize being used. Cerakote on threads is a very big no no. Additionally, double stacked shims were improperly used to align the barrel nut along with evidence of uneven shimming.

2. The barrel gas block port was incorrectly sized along with improper gas block assembly. Specifically, the gas port was measured at 0.081", which is incorrect for a 20" 1:10 rifle barrel. For a 20" 1:10 308 WIN barrel, the port should have been 0.093-0.096". My guess, the person drilling the barrel didn’t realize the barrel was not 16/18”, for which the 0.081” is appropriate. Additionally, upon inspection, the gas block screws were installed hand tight without threadlocker or dimpling.

3. Upon inspection, the barrel chamber showed machining marks or other surface defects from nitride treatment and/or factory polishing. This is further evidence of poor quality control during the assembly and testing process.