Who has the Brownell's 18" 6.5 Grendel barrel? What buffer, spring, gasblock setup?

[TacBlade]

I have this barrel/ bolt. I have the standard JP Silent Spring and a non adjustable gas block. It's throwing brass at 1:30 and does not lock back after last round. I have tried all weighTS of springs that JP offers and no changes. Also added one tungsten weight to the JP buffer. I have not tried an adjustable gas block. Let me know what you are using and where your brass is flying? Thanks!