This is the .577 Tyrannosaur (T-Rex). Properly named, as this cartridge will stomp on you like a Dinosaur in heat!
Just slight smaller than the .50BMG. Unlike most rifles that chamber the .50BMG, the gun that chambers this .577 T-Rex doesn't way 50lbs. It's a hunting cartridge and the gun needs to be "packable" for safari hunts. So, the result is a VIOLENT (knock-you-on-your-ass) recoil, especially for those who are not bracing for it. LOL.
Is there something more powerful and used for hunting??? Yup. The .600 Nitro Express. Just slightly larger than this .577 T-Rex. Now imagine this .600 Nitro Express... as a handgun.
If you listen closely, on both videos, you'll hear two pops! First pop is the gun firing. The second pop is the gun smacking the shooter in the forehead. LOL.