I was asked to make the tests by the editor of a major magazine, while doing an article on the effect of heat and cold on rifle ammunition. So I did, partly because he thought we should try some early factory ammo, because of all the stories about "hot" lots.
Some very early ammo may have been pretty warm. The sample I tried wasn't first-year production, and still resulted in higher muzzle velocity than more recent ammo. It was also well above the factory listed 2400 fps from a 24" barrel, despite my test rifle's 23" barrel.
As I recall, part of the "problem" with broken extractors on .416 700's was traced to poor rifle maintenance, resulting in dirty and/or pitted chambers, and bolt-faces loaded with brass particles. A long-time gunsmith I know has also found this to be a problem with 700's: The vast majority of the broken extractors he's replaced have been on rifles that haven't been cared for very well.
Ross Seyfried used a 700 in .416 Remington Magnum for several years when working as a PH in Africa. He had no problems, but did maintain his rifle carefully.
