Is it true that factory 150 loads for the .308 will outperform 150 grain bullets in .30-06 and the 165 loads in .308 will be about equal to 165s in .30-06? Heard that the higher pressures of the .308 allow it to push lighter loads better. Obviously the .30-06 is better for 180 grain and up. I read this online somewhere and am not an expert on ballistics.
I’ve owned and tested a couple of dozen 308 and 30-06 rifles over the last 15 years or so. The answer to your question(s) is a solid maybe.
Several years ago, I compared a bunch of factory 308 and 30-06 ammo in a pair of Tikka T3s. The differences between them got less significant with every test.
• The 30-06 averaged 78 fps faster with 150, 165, and 180-grain bullets.
• The 308 had less recoil and barrel heat.
• The 308 was more accurate.
But you need to look at performance in more than one rifle. The fastest 308/150 factory load that I found goes 2,886 fps from the 22” barrel of a Remington 700 but only 2,705 out of the 23.5” barrel of that Tikka. The fastest 308/180 factory load did 2,630 fps from the Tikka by only 2,561 fps from the Remington.
The slowest 30-06/150 factory load did 2,807 fps from a 22” Ruger Model 77 but 2,984 fps in a 24” Model 700 Package Rifle. That M-700 also shot the Winchester 150-grain Power Point load at 2,929 fps. 150-grain Greek HXP 30-06 military ammo sold through the CMP seems to do 2,700-2,750 in every 30-06 I own, which is a special kind of magic.
In the 22” Ruger (and in most other 22” barrels) most 30-06/180 factory loads did just over 2,600 fps. Winchester 180-grain Power Point factory ammo routinely clocked 2,700 fps in a 24” Model 70 Classic and a 24” commercial FN Mauser and 2,650-ish in a couple of 22” Husqvarnas. Remington’s 180-grain CoreLokt load went 2,712 fps in the 24” 700 but only 2,673 in the Model 70 Classic. I have not had the best accuracy with hyper-velocity loads in the 30-06. Several of Federal’s older loadings were 1-200 fps above what you’d expect for the 30-06 but accuracy was about 3 MOA. Hornady Superformance did 2,775 in the 24” Model 700 Package rifle with slightly better accuracy.
So here’s what I learned:
• Most factory 30-06 ammo is somewhat underloaded. Most factory 308 ammo is not.
• A fast 308 can match or slightly beat a typical 30-06 with factory ammo. A fast 30-06 outruns the typical 308 by about 100 fps. It takes a lot of testing to find out whether your rifle is fast or not and it's probably not worth the trouble.
• Trajectories of the 308/150 and the 30-06/180 are very close to being the same.
• The 308 tends to be more accurate.
• Handloading increases accuracy in the 308 and speed in the 30-06, but probably not enough to matter.
Okie John