I can tell you about the REAL difference between the .303" and 7.62mm extractors. It's all to do with the primary extraction. If you convert a .303" extractor to use in your 7.62 rifle, due to the geometry, the extractor will not grip the front edge of the thinner rim until primary extraction is almost complete.

Using the correct extractor means that as soon as you start to lift the bolt handle the re-designed 762 extractor will grip the rim sooner and you therefore get the CORRECT leverage and therefore perfect primary extraction. More to it than that of course.

Now for the official CHS, straight from the Indian EMER as obtained for me by the Indian Army Liaison Officer at Warminster. I ain't got it handy but I have written it down on an earlier thread and given the relevant gauges that are the closest to it