So, I tried troubleshooting the 5.45 AR with a thorough cleaning and replacing the formerly upgraded extractor spring, along with an H2 buffer. It ran slightly better on that combo. On a hunch, I’d ordered a new 5.45 complete bolt and it arrived yesterday,
as I was shooting. That bolt fixed everything. I can’t see any visual differences on the extractor and the bolt face is the same measurement between the two. I will check gas rings next. I should probably install
this Strike Industries adjustable gas block that I’ve got lying around as well.
Anyway, at least it’s running again.