Have you tried using the Tubbs flatware spring with the heaviest buffer that will reliably cycle your ammo. Also a F/A BC. Add mass to delay the intiation of bolt unlocking. Short of moving the gas port or using a spiral wound gas tube adding mass on the backend is the only easy way to delay unlocking.My AR10 will put a swipe on pretty much anything regardless of charge weight unless I turn the gas completely off. I reuse it. The brass life is short enough in that gun as it is.
The brass life...I wonder what the chamber vs virgin brass setback/headspace is? Then again it may just be so large in diameter measurements you would need a custom die to not over size it. On my hunting ARs I set case shoulder to 0.003" even have used 0.002" without issue. But my barrels are custom with tighter chambers that fit more like our bolt guns. All my 16" and longer are using rifle length or longer gas port locations. The real issues are anything with smaller caliber size than 30 cal.
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