I don’t have experience with the SpringCo in a 308 AR, only the AR15, sorry. The spring I ended up using was the Wolff one Clint recommended I pair with his XH buffer.
As others mentioned, your rifle is over-gassed, and my recommendations are keeping with your desire to not have to swap your pinned GB, which I understand. I would just spend the $125 and get the XH buffer and matching Wolff spring. You could also try swapping the extractor spring as was mentioned but my hunch is you need to slow your carrier cycling rate.
I will add that in my experience with my Mega Maten, I built it with a Superlative Arms adjustable gas block with MidLength gas on a Mega 16” barrel. I never bothered to measure the gas port, however a midlength was definitely less than ideal with cycling. Despite me opening the gas block screw all the way out, I was getting the same malfunctions you were as well as double feeds/FTE. I could also feel the impulse from the bolt cycling was harsh. Once I swapped bolt/spring my problems went away and I have perfect cycling and brass ejection at 3:00-3:30. I use the same suppressor you do BTW.
The added benefit with my troubleshooting is my AR308 has become very soft shooting but still reliable with all my handloads as well as factory 308 and MEN milsurp.
My malfunction before I swapped buffer/spring.
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