Wow,..this thread has come along way. A lot of great posts and pics regarding perhaps the 2 of the best .30s on the market.
Some are using factory published ballistic data as a comparison of the 10-20% gain in a similar barrel and action of the .30-06 over the .308Win. This should be the case,..ask any handloader of both cartridges, however........
I've not done a side by side comparison in years, but I remember years ago when if you had say a M70 in both calibers, or say a Remington 7400 in both calibers, and you chrony'd both with same ammo and weight, they were essentially the
same cartridge

. This is strictly from memory and if anyone has any current apples to apples please share them and correct me.
Fast forward 20 years, and I haven't done a head to head comparison of like action types and barrel lengths on the newer premium loads, which I believe live a little closer to where their makers say they are.
Again I know that unless you use the same actual barrel for dimensional purposes and therefore pressures, you couldn't really compare a factory Core-lok 150gr in both calibers.
Just something I noticed when I believe the '06 was for years intentionally loaded below the already conservative factory ballistics, for safety concerns in much older and questionable headspace and receiver strength(1903). The .308 seemed to always be doing what everyone said it should based on your particular barrel length.
Anyone else do a side by side comparison recently of both cartridges in similar action and barrel length's?
So this post doesn't get corrupted by some thinking I'm saying the .308 is everything a .30-06 is,... it's not intended for that.
Apples to apples, the '06 just has a bigger case and will produce higher velocities at SAAMI pressure levels.
Just be sure you know your actual factory velocities before betting too much money on a particular round based on factory published velocities.
A chronograph is the final say on velocities. A lot of the "go to" factory loads because of accuracy, and even game getting ability, rarely come close to published data over the chrony in real world testing.
An example was when I zeroed a lovely Parker-Hale sporter for a guy while I had my chrony set up for load development.
The published data was 2480 fps in a 24" test barrel for 180gr Winchester PPSP, but in the 24" cut, new No4 barrrel, those 180 power points were loping along at 2260 +/- 20 fps. Deadly accurate with a tight extreme spread, but a far drop from a 22" .308 sporter firing the same ammo weight at nearly 2600 fps.
The .303 at this actual velocity was approaching the .30-30 /170gr @ 2200fps ballistics data, of course they never achieve this either in the real world.
I decided to fire away some old handloads through my 22" .270Win over the weekend, and over my chronograph at 15 feet center I got these velocities compared to published data.
Winchester 130 grain PPSP average 2880. Published data 3060fps in 24" so should be around 2990 in mine. Down 110 fps
Winchester XP3 elite 130 gr average 2945fps, Published data 3050fps
should have been around 2980 in mine so closer. Down only 45 so okay.
Handloads from 1992 season

, 130gr Sierra BT @ 59 grains IMR 4831/CCI250
average 3087, low 3072 high 3107. Was that a 270 WSM we just passed daddy? Yes son,..it was.
Is my chrony clocking low? I get 2800 average with NATO 147FMJ from a 22" barrel M-14, so I'd say it's very close to being on.
After all this rambling, I guess I'm going to have to get "like ammo" for both my semi's, and do some side by side velocity testing with modern premium ammo.
Anyone else up to doing a side by side, same rifle/ same barrel .308Win versus .30-06 testing?????? Please publish your data if you do.