Well, ok.. go try to find a factory load of 6mm Rem. using light bullets. And then do the same for 243 Win. So yeah, I look at things as they ARE. Not what they “might” have been, or thought to be 50 years ago.

Overbore and speed(which typically go hand in hand) are the enemy. And as Fred point out, Heat. More powder, smaller bullet, more speed all equal more heat. Case shape and even neck length have no conclusive evidence backing up their argument. It’s all Anecdotal. Sorry, I just really hate anecdotal evidence used to prove something. And so many do it.