.577 Tyrannosaur

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577 Tyrannosaur
577 tyrannosaur.png
577 Tyrannosaur
Place of originUnited States
Production history
Case typeRimless, bottleneck
Bullet diameter0.585 in (14.9 mm)
Neck diameter0.6135 in (15.58 mm)
Shoulder diameter0.673 in (17.1 mm)
Base diameter0.688 in (17.5 mm)
Rim diameter0.688 in (17.5 mm)
Rim thickness0.063 in (1.6 mm)
Case length2.990 in (75.9 mm)
Overall length3.710 in (94.2 mm)
Rifling twist1 in 12 in (305 mm)
Primer typeLarge rifle magnum
Maximum pressure65,000 psi (450 MPa)
Ballistic performance
Bullet mass/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): Alphin (1996)[1]

The .577 Tyrannosaur or .577 T-Rex (14.9×76mm) is a very large and powerful rifle cartridge developed by A-Square in 1993 on request for professional guides in Zimbabwe who escort clients hunting dangerous game. The cartridge is designed for use in "stopping rifles" 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.


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

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