Reboring a barrel to a larger caliber typically ends up with less accuracy than the original.
Custom barrels typically have an inch or two cut off their muzzle end to get rid of the poor rifling quality in that area. Chamber reamers remove the bad stuff at the breech end.
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master