From my phone calls and probing and talking to an engineer here and there at a few ammo plants over the years, I have found out generally they use the exact same thing we have available.

Only a few of the new calibers and weatherby rounds are really blended.

You could definately narrow down the powder with alot of time or patience, and sometimes they will tell you if you get a hold of the right guy. You could tear apart a few, wieght it, chrono it, measure its density, and come close. IMR has always been a big distributor for Remington.