I have loaded some H1000 in a couple of calibers, one of which was the 338RUM, and found it to be a sort of strange powder. I am not surprised by the results you have posted above but don't have any answers concerning this. One thing I will say, if you get into a compressed load situation you probably won't like the results. I loaded some 270Win with 140 grain Hornady bullets and a full case of H1000 and took them to the range the next morning and shot five of them into a single hole and thought whoopee I have found "the load". I loaded up a bunch of these and took them deer hunting and though I didn't miss any deer I shot at they just didn't seem as accurate as when shooting them previously at the range. I then took the same ammo back to the range and instead of a one hole group it shot a 3" group instead, so when I got home I pulled a bullet to see what happened and the powder was one solid brick and had to be chiseled loose to dump from the case. It is as though the coatings never dry and when compressed just glues into one solid blob. I have switched to H4831 and though it doesn't shoot as good as the H1000 initially did it does perform very well. BTW, H4831SC is, I am satisfied, the powder that Remington loads their factory 250 grain loads with. i.e. 89 grains of it, but they would never admit this.
