It's a slow-burning and very high energy double-based ball powder usable as an alternative to H4831. When it first arrived I and a few others tried it in 284 Win heavy bullet match loads. We got high velocities and good results - sometimes. It didn't prove consistent enough in this role. As
@badbob says, it should be well matched to the 243.
It and its faster (approx. VarGet speed) burning stablemate Hodgdon Leverevolution are Reach compliant and still with us. I don't think they sell too well - I tried to get some Leverevolution recently and the distributors Edgar Brothers don't have any and were apparently a bit vague about future orders.