Hate to point out the obvious, but that WR in 500grains' post appears to be chambered for the .577/.450, which is probably the old black-powder Martini-Henry cartridge, not the .500/.450 NE. Even the express load in that cartridge is no comparison with the .470!

No personal experience with the Blah-zer but share 500grains general sentiments. IMHO Brit is usually best.