A 308 does not a 30-06 make.
If your shooting 165gr bullets, fine, but the 06' is still faster hence flatter shooting, carrying more energy.
Go above that weight and either your impedeing into your powder space, or need a long throat in the 308. Either way your still not getting quite the performance as the 06'.
Don't get me wrong, i like both cartridges. But there is a performance difference, especially if you handload.
I may be incorrect (probably am), but i thought most "featherweights" had a 20"barrel. How they shaved 1/4 ounce.
