The thing is that the FC cases are very thick, and soft... not really good for repeated reloading... loose primer pockets will be the norm. And you'd of course have to be using FC cases if you're planning on duplicating their load. In winchester brass, you'll need more than 44 grains of RL15 for a good match load that will fly like the Federal load does (the FC cases are tighter on the inside, so less powder will make more pressure).
So whatever the powder is (and yes, it's almost certainly RL-15, we're here next to the Radford Army Ammunition plant, and all sorts of ATK components are spoken... and revealed...
...but, you won't simply be able to put that amount of RL-15 into any other case other than the FC cases (working up from published data, of course... watching for pressure signs of course... and realizing that your lot of RL-15 may not be just like Federal's lot)...
If you want to blow the doors off the Federal ammo, get some Winchester brass and work up to 43.6 grains of IMR 4895, using any good 168 grain match bullet. You won't be looking back...
Dan