I don't know, I guess it's all in the powder you need to get the pressure for a clean burn with a 30 grain Berger. I would bet that H4895 would be close to the right powder but it won't fill the case. All the powders for the BMG are too slow for the light bullet so H4831?
I think the round would be a reloaders nightmare.
We could just fill the case with H1000 and push a bullet in to see what would happen when somebody we don't like shot it. I think it would push a flame about 10 feet out the muzzle and the bullet would race away at nearly the speed of sound. Like a fizzled M-80.
On the other hand with the slow rifle powder it might go PPPPHHHHHHT BOOOM! Throwing the bolt through the shooters lower jaw and various pieces of the rifle through extremities.
It would be real interesting to watch - from a distance - but not much fun from the shooters perspective.