Bonanza, many rifles with worn , or burned bores are good shooters. The reason they effect value so much is, the life of those barrels are almost used up. When you consider a double rifle with a burned bore, that is already 100 yrs old, still shooting well, but if the bore was brite, and sharp, it would shoot well for another 100 yrs. It will not if the the barrels are on their last legs, and the cost to re-barrel a double is quite expensive. The re-barreling of a double rifle also advercely effects the value, though it may actually be a better shooter than it was when new.