Shooting .257 Roberts in a .6.5mm barrel would be a waste of time as the bullet would barely touch the rifling. The original barrel will have a groove size of about .265 or more . The rifle should be in 6.5mm Roberts if it was done correctly , and that is a handloading only cartridge . If is really just done in just .257 it is not go for much . Rebarreling a Type 38 is not easy as the barrels are hard to get out , a used one will not index without work . If you go with a barreled receiver it would be easy to make a correct looking shooter , but you would lose matching #'s .