You're absolutely right edi on many fronts, the difference is in the recoil and the bullets. A 143 6.5 bullet has a g7 bc of 0.315. A 155 Scenar in 308 has a bc of 0.234. At long range that's a lot of lost velocity/energy and significantly more wind drift than the 6.5. The 6.5 has a lot less recoil than the 308 as a bonus. It's a pussycat to shoot.
The 308 has proven itself to be one of the most accurate cartridges ever designed, but I believe that as bullet design has moved forward so rapidly over the past few years there are a few better options out there now, both for LR and hunting.
The 308 has proven itself to be one of the most accurate cartridges ever designed, but I believe that as bullet design has moved forward so rapidly over the past few years there are a few better options out there now, both for LR and hunting.