The problem with using a cleaning rod and hammer is that, unless diligent care is used, the cleaning rod could (even though it is normally softer metal) disfigure the lands of the barrel.
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)