Sorry guys, can't say, because I don't know! Actually, I'd hazard a guess that there's probably several. Bear in mind that most of my experience with this is with our domestic manufacturers, both civilian and military. In loading the M118LR at Lake City, for example, there's several powders that have been used. No difference in specs, performance or designation, but many different powders. Right now, it's RL-15. For many years before that, it was WC-750, and before that, IMR4895. There have been others as well. The bottom line is, specifications; the load has to deliver X accuracy at X distance, X max chamber pressure, X velocity, X port pressure, and X variance in velocity at so and so temp extremes, etc.. Any powder that meets this criteria may be used to load that ammo, depending on availability, customer demand and a whole host of other things. Same thing holds true from civilian ammo producers. There's a range of powders that may meet the criteria for the finished ammo, and they may use several different types for any given cartridge. They do this in part to assure that they won't be shut down on production if there's a shortage of some particular powder. At any rate, many of these are (as I mentioned) non-cannister grade powders, custom blended for that run and not available to the handloader anyway.
Sorry guys, but no simple answer here.