I'd go DI with an adjustable gas block like JP or SYRAC. DI tends to be more accurate than piston setups for the most part. I would imagine even more so on a 308, where the bolt carrier assembly is so much heavier than a 5.56. The piston pushing against that heavy carrier would be even more prone to side loading the barrel under recoil.
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U.S. Navy (Retired) 1994-2015
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