"Comparing the .308 (which is a fine round) to a 30-06 is probably not a good choice. The only thing they have in common is the caliber/bullet diameter. The muzzle velocity and energy of the 06 is superior and therefore broadens the range of game animals that can be ethically taken."
These two cartridges are very similar. Especially the military versions.
You cannot notice the differences in accuracy at ranges under 1000 Yards. Most hunters will require a 600-800 Yardage. The 30 06 Vs 308 ballistics are practically the same within hunting range. Past 1000 Yards, however, there is a lot of visible difference on the 308 Vs 30-06 Ballistics Chart.
So, the 308 clearly beats the 30-06 on accuracy.
The 308 has less recoil than the 30-06.
Finally, despite all the modifications you can make, the 30-06 trajectory will always remain similar to the 308's trajectory.
Where the 308 Winchester struggles slightly to keep up with its counterpart is in the muzzle velocity department.
The reason being that it is able to accommodate more powder.
On power, none of the two has a clear hunting edge. Both provide more than enough power to bring down big game like elk. In short, both are equally useful when it comes to hunting big game.
In a nutshell, the 30-06 and 308 are too similar to merit a change into either.
but IMO the best all around cartridge ever!
As an opinion its an opinion and it is for the individual to judge. For me there are simply too many cartridges that are so drastically similar and will do what 99% of their users ever intend to do that there is no functional difference.
Start somewhere above the .243 and end somewhere below the .338 magnums. The various cartridges that fall in there are, for the most part, so close to each other to be indistinguishable except for some niche use.
To the OP's question of "Why not the 30-06" all one can do is shrug. But you can sub in any number of cartridges there and get the same response.
I'm guessing others can say that the __________ did it before the 06 too.
As much as I enjoy the .30-06 Springfield (especially out of a 24" Bbl'ed 10.5 lb. M1 Garand)?
I think that the .270 Win is a "better" optimized cartridge for a sporter rifle for medium to large game.
It shoots a 150 gr. bullet at nearly the same velocity as the '06, but that bullet has the BC and SD of the 180 gr. variety, so you get the performance of the heavier bullet with generally accepted tolerable recoil (in the light weight sporter rifle).
I disagree. Looking at my old Hornady fifth edition handbook, I find six loads (150-155 grain bullets) that reach 3,000 fps. with a 24 in. barrel whereas, the same handbook shows only two loads that hit 2900 fps. with 150 grain bullets. What is notable, is that the loads for the 06 are not likely over the SAAMI limit for the 06 of 60,000 psi. whereas the .270 SAAMI limit is 65,000.
Therefore, if a person hand loaded the 30-06 while watching for pressure signs instead of trying to stay at the SAAMI limit as per the handbook, one could conceivably get the velocity (safely...both pretty much the same cartridge case, in modern rifles), even higher than the 3,000 shown in the handbook.
No one said anything about comparing a 180 grain 30-06 bullet to 130 grain .270 velocity. That seems to be a strawman argument.But you are never going to drive a 180 gr. 30-06 to the velocity levels of the 150 gr. .270 Win, while retaining the same lower recoil levels.
Because that is what the .270 Win./150 gr. does.
No one said anything about comparing a 180 grain 30-06 bullet to 130 grain .270 velocity. That seems to be a strawman argument.
Also, no one suggested shooting either cartridge at unsafe velocities ("thermonuclear")...hand loaders have been increasing powder amounts until pressure signs appear as a standard procedure for years.
The pressure "limit" imposed by SAAMI of 60,000 psi on the 30-06 was for the benefit of the old rifles still in existence and being used. A modern 30-06 would not be in any more danger at 65,000 psi than any .270. In short, the velocities posted in loading manuals for .270s are already near their pressure limit whereas the velocities listed for 30-06 are not.