The first bullet I'm going to try is the Badlands 275gr SBII and it says 1:9 will work, but it's barely above the 1.5 stability. It got be wondering if I should go with a faster twist and at the same time I would hate to go to fast and not be able to shoot cup and core bullets.I would stay around a 1:9 twist depending on the weight/length for .338. Best results for a Berger 300gr-OTM is in a 1:9.35.
Just an opinion.