Dan,
Unless I totally misunderstood your OCW load development system, replicating the velocity of an "accurate" factory load is pretty much irrelevant, no?
An almost infinite combination of powders and charge weights can deliver that end result- but it's the barrel harmonics/burn rate that's determines whether that MV duplicates the accuracy of the factory load (??)
So, if FGGM is a proprietary powder blend, the results could only be duplicated by trying to duplicate pressure curves with a strain gauge or similar?