Dave Scovill, from HANDLOADER magazine, has done a number of experiments on this subject going back many years. One caliber in particular, the 45 Colt, has been plagued by oversize chamber mouth dimensions due in part to Colt changing the barrel groove dimensions(smaller) but leaving the cylinder chamber mouths the same size(larger) resulting in a mis-match which could/did give the 45 Colt cartridge an undeserved reputation for mediorcre accuracy. In almost every case, Dave found the best accuracy came when he sized lead bullets to the chamber mouth dimension.Upon firing, the bullet base would obturate while still in the cylinder and swage down to correct sized as it made its trip down the barrel. Of course, all this assumes the correct bullet alloy, bullet design,powder charge etc. Colt wasn't the only manufacturer to use these somewhat mismatched throat/barrel dimensions, but point being accuracy improved when sizing the bullet to fit the chamber mouths.
If the chamber mouths happen to be smaller than barrel groove specs, then reaming out the cylinder as you mentioned would definatley be the way to go if top accuracy is desired. Otherwise, trying to get good accuracy from such a combination is likely to drive you crazy and make you think about taking up a different hobby.