Some folks may be interested in knowing that the .308 Winchester trumped the .30-06 for long range matches back in 1964. Yes, the '06 shoots a given bullet faster. But the .308 was (and still is) more accurate. Accuracy is how close together the bullet holes are at the target, not how little their trajectory arcs.
Yes, GySgt Hathcock used the '06 in 'Nam. It was the only cartridge the USMC Win. 70 sniper rifle was chambered for. When he retired from active duty, the folks at Quantico MCB checked his sniper rifle for accuracy; it shot about 20 inches at 1000 yards with M72 match ammo. He preferred a 30 caliber magnum for competition at 1000 yards as the USMC's .30-.338's and .300 Win. Mags were much more accurate.
That M2 military match bullet, while the standard for many years in both .30-06 and 7.62 military match ammo, was not all that accurate compared to what Sierra Bullets had to offer for the .30-06. Most lots of 30 caliber M72 match ammo tested in the 8 to 10 inch range at 600 yards from bolt action test barrels. Folks hand loading Sierra 190 and 200 HPMK's in their .30-06 could get 5 to 6 inches at 600. 'Course along came the .308 and test groups went down to 3 inches with Sierra's. Neither the M72 nor M118 match round was/is competitive along side Sierra's or Berger's 30 caliber match bullets. Even the military teams knew this and preferred commercial .308 Win. match ammo to use in their 7.62 NATO M14 and M1 rifles. Back when the 30 caliber Garand was the only rifle allowed in service rifle matches, folks bought Winchester white box match ammo that easily out performed the M72 round accuracy wise.
Note that after my good friend set the 1000-yard match record at the Nationals with a borrowed 7mm Rem. Mag. in 1970, that cartridge instantly became "the" one to use for long range competition. Problem was, Sierra had problems getting jacket material good enough to make bullets very uniform so they would shoot accurate.
It took another 10 years before consistantly good rolls of copper sheeting could be had for small caliber, long heavy match bullets. And it was another 8 or 10 years before 6.5mm match bullets were as good as the old 30 caliber ones were. When this finally happened, the 6.5-308 and 6.5-.284 became the favorite in high power competition. They were much easier to shoot accurately from the shoulder because they had less recoil while the bullet was going down the barrel.