I don't know i never heard of it but i sure wouldn't want to shoot it.lol
this is what i found out about it,,,, Must be some big squirrels in Africa
From Wikipedia: The .577 Tyrannosaur or .577 T-rex is a cartridge developed by A-Square in 1993 for the hunting of large game in Africa. The .577 contains a .585-inch (14.9 mm) diameter 750-grain (49 g) Monolithic Solid Projectile which when fired moves at 2,460 ft/s (750 m/s) producing 10,180 foot-pounds force (13,800 J) of energy.[1] The production model from A-square is based on their Hannibal rifle platform