.577 Tyrannosaur

The 577 Tyrannosaur or 577 T-Rex is a cartridge developed by A-Square in 1993 for professional guides that escort clients hunting dangerous game. The cartridge is designed for use in "stopping rifles": A rifle intended to stop the charge of dangerous game. The 577 contains a .585 in diameter 750 gr Monolithic Solid Projectile which when fired moves at 2460 ft/s producing 10180 ft.lbf of muzzle energy. The production model from A-square is based on their Hannibal rifle platform. This cartridge has the distinction of possessing the heaviest free recoil of all commercially available, shoulder-fired weapons, at 220 lbs into the shoulder with its heaviest solid of 750 grains. The larger caliber, .700 Nitro Express, drives a 1,000 grain solid at 8,900 foot-pounds, with free recoil of 200 lbs into the shoulder.