Not totally. My expectation, and of course it's only an expectation, is that the bullet manufaturer takes into consideration the speed and energy of a particular cartridge when it designs how quickly it mushrooms. So is it possible that they would design two bullets of different caliber tomushroom similarly while passing through an animal? If that were the case since the 30-30 is a larger diameter the wound channel would be bigger.
Well if thats true then the 30-30 would have a bullet that fragments easier than the .243 making it worse for you you brush busters.