I think external adjustments are a little fragile
Not that we ever want to hit our rifles or scopes on anything but I think that the externel adjustment models I have seen looked more fragile. It is really cool that you have that Model 70 to shoot. I wonder if the twist rate has changed over the years on the 243? I know that Remington made a mistake with the picking the wrong twist rate on the 244 Remington later changed to a faster twist and called it the 6mm Rem. I will bet that you will be having fun shooting 95-100gr bullets in yours. Recoil will be non existant.