Recently, "Dave D." wrote to Sharpshooter and asked:
"... Do you prefer the .308 or .30-06? I understand the military is very keen on the .308, though I suspect it's because they have a much bigger abundance of that than the .30-06. I've read that in tournaments, the .30-06 excels, due to a heavier projectile and more powder in the cartridge."
When people communicate to me, via written correspondence, I take the words they use very literally. So, when you say "prefer," I have my own "preferences" which may not reflect those of others.
Personally, I prefer the .308 Winchester/7.62x51mm NATO cartridge, but I must explain why. It is not because the .308 Winchester is more "accurate" than the .30-06 Springfield/7.62x63mm NATO cartridge, but because the .308 is more commonly available in today's market as GI brass and surplus ammunition. For this reason (availability), my tactical rifles are chambered in .308. If I ever need to survive in a domestic environment in which I may have to procure ammunition through other-than-legal methods, I'll probably have a better chance of getting my hands on vast quantities of .308 ammo rather than .30-06 ammo.
Years ago, the military decided that carrying around sufficient quantities of the larger cartridge was just too much weight for a soldier to hump around with, especially when coupled with the weight of the rifle that fired it. Without going into the politics of the period, the M14 was adopted as the service rifle of the day, with the shorter and lighter cartridge. However, shortly afterward, the M16 started replacing the M14 as the military's service rifle and, without arguing on points of ballistic performance, the rifle -- and the ammo it used -- weighed significantly less than what had been previously issued.
When people compare the .30-06 against the .308, they usually don't do so in a scientific manner. A proper comparison should account for "time" -- then and now. With the powders of the day, when the .30-06 came into being, the way to achieve higher velocities and to shoot farther was to use a large case filled with powder. Over some years, powders improved (and of course, speaking of powders, you are aware that "IMR" stands for "Improved Military Rifle") and large cases were no longer absolutely necessary to meet the performance requirements of the military. Enter, the .308 -- with it's smaller and lighter package, it could do virtually the same job as it's big brother without weighing as much. And popularity? Well, whether it's based in a survivalist mindset or not, civilians tend to rave over whatever ammo and weapons the military are using. So, it was natural (and expected) that civilian shooters would welcome the .308 as "the" round of choice for .30-caliber shooting.
Given today's powders, the .30-06 has definite advantages in distance and energy over the .308 for any given weight of bullet. However, these advantages are only realized "in the extreme," and for most hunters' and target shooters' applications, there's very little difference in performance. Considering that many shooters handload their own ammo, it is no wonder that the smaller case is more in demand. When surplus GI brass can be acquired so inexpensively, why spend more money for .30-06 cases? Where economics are concerned, the .308 wins -- hands down.
I mentioned extremes, so let's talk about them a little. I've always believed that the .30-06 is probably the most versatile cartridge on the planet. Using extremely light bullets, it makes for a lethal varmint round. Using heavier bullets, some of the biggest game on Earth have fallen to the .30-06 on several continents around the world.
Handloaders, using some of the modern, lower-pressure/higher-velocity powders (such as those in Vihtavuori Oy's 500-series) can truly wring out the maximum performance of the bigger cartridge. In such a case, the .308 will always take a back seat. However, let me be clear about this -- I am, again, talking in terms of extremes. Most responsible hunters take game at "reasonable" distances, and the farthest that most target shooters compete at -- in NRA-sanctioned meets, for example -- is 1,000 yards, a distance that has been easily handled by the .308 cartridge for many years now.
So, for my .30-caliber shooting needs, I'll take the .308 Winchester over the .30-06 Springfield. It's accessible and does the job.