I've a rifle the best group its ever shot w/me or any one else is a 3 shot 2"w/ factory ammo, some of them missed an 18"sq at 50yd. Conversely I've a friend w/1 that's never shot over 4" or 8" from point of hold. W/that said, and you having by now rechecked all of the rings and mounts,I will suggest checking that the bbl and stock are either in full tight contact or having no contact. Also that the stock/action screws are tight. Some rifles just don't shoot well full floated.1 more thing, check the muzzle crown I know it is a new rifle but the right/wrong bump will do 1 in and cause just what you discribe