buttstock,
You have several misconceptions about this subject:
1) There are at least a couple of pressure-tested sources of data that show if not EXACTLY 2700 fps for 200-grain bullets in the .30-06 from the standard SAAMI 24" test-barrel, but within around 10-15 fps.
2) These data sources adhere to the long-time standard 60,000 PSI Maximum Average Pressure (MAP) for the .30-06, which is somewhat lower than similar cartridges, due to the older rifles chambered for the .30-06. As one example, the .270 (the .30-06 necked down) has a MAP of 65,000 PSI--and there's no reason a modern .30-06 would explode at 65,000. According to the basic rules of interior ballistics, another 5000 PSI would add around 100 fps.
3) No, a longer barrel does NOT result in a "more complete burn" of modern powders. You're apparently a victim of long-time myths/assumptions. Modern powders essentially burn as much as they're going to within 2-3 inches in front of the chamber. The added velocity from a longer barrel is a result of the powder gas continuing to expand down the bore.
