The reason that bullet didn't exit isn't because you are shooting a 308, it's because that bullet is light and expanded quickly. A standard cup & core 150 most likely wont fully penetrate any chest cavity shot with any 308 (or faster) cartridge. I don't subscribe to the "bullet dump" theory and would much rather have full penetration and instant external bleeding vs waiting on an animal to internally fill up before it may or may not begin leaving a consistent bloodtrail. If you want to shoot 150s in your 308 but have consistently reliable and instant bloodtrails then I'd recommend you try the solid copper bullets like Barnes, Federal Trophy Copper, Hornady GMX, Nosler Etip etc... If you want to stay with traditional cup & core bullets like your Federal softpoints, Rem CoreLokts, WInchester PowerPoints etc then I'd recommend you go up to 180s in your 308.