Freedom Arms developed the .454 Casull back in the late 1950's. It is basically an extended and strengthened Colt .45 case with a powerful punch. The round is fitted with a small rifle primer and a progressive burning powder. Both of which allow for an increase in the chamber pressure and therefore the velocity and energy delivered to the target.
Like the .357 Magnum, which is an extended and strengthened .38 special, the .454 can chamber and shoot the smaller, standard Colt round...And just as a .38 cannot fire the .357, the same holds true for a standard Colt .45 and its bruiser big brother.
Both Sturm-Ruger and Taurus of Brazil have built pistols chambered for the massive .454. Both manufactures have included a muzzle brake to help tame the powerful recoil.
The pic above is the Ruger iteration chambered for the .454 Casull.
Here's a visual aid for comparing rounds. On the far right is a .22 long rifle. On the far left is a 3inch, 12 ga. round. The .454 Casull sits just to the right of the "AA" battery.
What are the rounds between the 'lil .22 and the "AA" battery? I'm glad you asked!
Right to Left:
.22 long rifle
9 mm Luger
.44 Rem. Magnum
.45 Win. Magnum