I shot my daddy's pre-64 Model 70 in 30/06 when young but my first CF rifle I owned was a Marlin 30/30. I have the old model 70 but traded the Marlin sadly. I load for it and many rifles now hunting more and shooting less.
I have zero experience hunting with an 8mm Mag and will let those that do fight out its ballistics and usefulness but I have a quick story to share. While groundhog hunting back in the early eighties a small group of friends we ran across a hunter sporting a 6mm Rem. We got into a conversation...
Ideally I want the bullet to expend as much energy inside the animal leaving enough to exit the opposite side. I realize different ranges will dictate how this happens so matching the cartridge/bullet to the game and area hunted comes into play.