DarthAlucard
It is impossible to have a .454 Casull in a (semi) automatic design. the stress alone would shread the gun apart. The small parts would not be able to handle the stress. But yes, there is a .454 casull, but it is a revolver round.
I think what they mean about it being a .454 Casull is that it uses a modified .454 Casull round and is a handgun. The very fact that the original .454 is a revolver means that it couldn't be modified to be a semi auto - if it -was- changed to semi, it would be a completely different weapon.