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577 Tyrannosaur
577 tyrannosaur.png
577 Tyrannosaur
Type Rifle
Place of origin  United States
Production history
Designed 1993
Parent cartridge New Design
Case type Rimless, Bottleneck
Bullet diameter 0.585 in (14.9 mm)
Neck diameter 0.6135 in (15.58 mm)
Shoulder diameter 0.673 in (17.1 mm)
Base diameter 0.688 in (17.5 mm)
Rim diameter 0.688 in (17.5 mm)
Rim thickness 0.063 in (1.6 mm)
Case length 2.990 in (75.9 mm)
Overall length 3.710 in (94.2 mm)
Rifling twist 1 in 12 in (305 mm)
Primer type Large Rifle Magnum
Maximum pressure 65,000 psi (450 MPa)
Ballistic performance
Bullet weight/type Velocity Energy
750 gr (49 g) Monolithic Solid 2,480 ft/s (760 m/s) 10,240 ft·lbf (13,880 J)
Test barrel length: 26 in
Source(s): A-Square Any Shot You Want

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-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 muzzle energy.[1] 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.


  1. Alphin, Arthur B. (1996). Any Shot You Want (First ed.). On Target Press. ISBN 0-9643683-1-5. 

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