Up front, I don't intend this to be a "DIAGNOSE MY MALFUNCTION OVER THE INTERNETZ" exercise. I realize the silliness and futility of such a thing.
That being said, I want to learn more about popped primers in the AR-15 system. I've had my current personally owned patrol rifle for about 4 years. It is a BCM 12.5" barreled upper and BCM bolt/BCG/CH above a no-name lower (believed to be an Aero Precision, rebranded). The buffer and action spring are the same ones that came in it when I bought the rifle from the company that assembled it for me four years ago.
This rifle has been shot quite a bit, but not an absurd amount. It's been through a 3 day Pat McNamara class, a 2 day Kyle DeFoor class, and three years of SWAT trainings that included firing range about once a month. I've not done any maintenance on the bolt/BCG, buffer, or action spring. No parts have ever struck me as needing to be replaced.
I started running it suppressed about 4-5 months ago with my Saker 7.62 with 5.56 endcap. In the past three months, I've had four popped primers (various quality ammunition, including Speer Lawman and Hornady, all 55 grain training style loads). In the preceding four years, I had zero (that I noticed or that caused malfunctions).
My gut tells me:
1) The action spring is getting tired, and isn't putting the same pressure on the bolt/BCG. This is allowing the bolt to move to the rear too soon after firing, and as a result is sending the higher-pressured gas through the casing and busting the primer out the ass. I should replace the action spring with a .... ?
2) The action spring was never strong enough to be used with a suppressor, and I've been running the ragged edge of functionality while playing with fire and popping primers without noticing most of the time. I should replace the action spring with a .... ?
3) Something with extractors or ejectors. Mumble mumble mumble. I should do.... ?
SO, I'm not trying to ask the internetz to diagnose my issue, but where should I start looking? Are there tests I can try to run and recreate issues to narrow this down? If I do have to replace an action spring... holy fuck. There is a LOT of conflicting and confusing information out there. How does one know what the proper spring is without buying 3 of them and shooting 1000 rounds through each? (I would rate this rifle as 97% reliable right now. I could probably shoot a whole day without issue... or not).
This was today's: