The BCG that I have bought from them, and the uppers that included BCG specified in detail all the materials. Of course, they were all the "premium" ones. I notice the none premium ones usually do not.
Here is a description I found. I will admit it is not as detailed as some of the ones I have purchased in the past.
"Made in USA. Bolt is made of Mil-spec Carpenter 158 steel, Shot peened, High pressure tested and Mag Particle Inspected. Gas key is machined out of bar stock, chrome lined phosphate coated, and secured with grade 8 fasteners and staked per mil-spec. Bolt carrier is phosphated outside and chrome lined inside. Laser engraved with the PSA logo.
Extractor Spring
Black Extractor Insert
Mil-Spec O-Ring
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