Indy,
1) As far as I know it is still a country free enough to allow anybody to load what they want to. But in general somewhat slowwr powders than H4831 will produce good velocities with heavier bullets.
What are the best powders for use with 26" barrels and 150, 165, 180 (especially) and 200 grain bullets? Are they the ones mentioned in your article?
Also, do you have any idea why the Norma manual should list a maximum charge for 180 grain bullets which was so much more than the safe maximum in your Vanguard? Is it possible that a MkV has more freebore than a Vanguard, allowing more powder without excess pressure? Were you using Weatherby cases? (I've found that Remington cases weigh about 20 grains more than Norma cases in this caliber, with less volume, obviously.)
