I would like to hear more about the new BP substitute. Any shooting experience? I have shot 577/.450 with 777 loadings and they are healthy. These were factory loaded by TenX. I have used 777 in pistol loads and in 12.7X44R. The Pistol loads are great. Clean, good velocity. The 12.7X44R is a full case up to a card wad and Hornady Great Plains 440 gr .50 bullet. Shoots well, with authority and pretty close to Sites in my SXS Combo. I don't have a chrongraph to check the speed.
Most BP substitutes I have read about are not very effective in cartridge loading. Pyrodex is OK, but I don't like the way it seems to vary load to load. And, I too worry of the corrosive action on my original bores.