RE: Lets be honest with powder charges.
Used to use very heavy charges of Pyrodex RS. Yes, 150 grains of the stuff and a .430, 240 grain XTP shot well: Groups were 1.5" to 2.25" at 100 yards. Found out that such heavy charges were not needed.
Currently my .50 guns use:
CVA Stag Horn: Two Pyrodex pellets or 100 grains of loose Pyrodex and a .430, 240 grain XTP.
CVA Magnum Hunter: 100 grains of 777 and a .430, 300 grain XTP
Encore: 90-120 grains of JSGand a 250grain SST.