Abstract: A method of making a catalytic converter includes providing a catalyst substrate having a substrate periphery and a mat support disposed thereon. The method also includes providing a metal shell having a shell wall having a shell periphery and a bore that is configured to receive the catalyst substrate and mat support. It further includes inserting the catalyst substrate and mat support into the bore of the metal shell in slidable engagement therewith. Still further it includes reducing the shell periphery while applying an axial force sufficient to cause translation of the catalyst substrate and mat support relative to the bore until the force reaches a predetermined retention force threshold, whereupon the reducing of the shell periphery and translation of the catalyst substrate is stopped.