The .470 Capstick is a wildcat with no official Hodgdon data, so everything's from handloaders and QuickLOAD guesses start low and work up carefully, watching for pressure signs flat primers, sticky bolt, etc.
Real world reports with H4895 and 500gr bullets Barnes, Woodleigh, etc.
One guy ran 72gr for 2260-2290 fps in a 24" barrel solid, accurate load.
Others pushed 85 -90gr for 2300-2400 fps, but that's hot compressed, high pressure.
Your 77gr starting idea is reasonable per some QL estimates hits 2100-2200 fps safe, but I'd drop to 70-72gr to play safe with the Swift A-Frame bonded, expands well
2300 FPS is doable cartridge goal, but expect 80-85gr max depending on brass/barrel test in 1gr increments.
No specific Swift A-Frame data, but it should behave like Barnes TSX. Use magnum primers, good brass Bertram Peterson. That velocity with A-Frame will wreck anything good luck!