Buffalo Bore Ammunition 7B20 Personal Defense 454 Casull 300Gr Handgun Ammo - 20 Rounds - The .454 Casull is one cartridge that Buffalo Bore Ammunition does not load to its full pressure limit because it can become unreliable and unpleasant to shoot. At upper pressure levels, heavy bullets tend to jump crimp - tying up the cylinder. Also, fired brass can stick in the chambers.