The original version had feeding problems, the bolt would hang up, sometimes. Look for a Win.670 with the "G" serial number. This was the final 670 version. It is smooth. The right hand locking lug has a groove in it that follows a rail on the inside of the action, so it does not and can not do anything but be buttery smooth in action. Many Bench Rest competition custom rifle builders buy this rifle for just the action. It is that smooth. Bench rest competitors do not want the classic Pre-64 Winchester Model 70 "Mauser" claw extractor on an action. It cants the cartridge case to one side, and will not fire as accuratly. Anybody that pans the 670, just does not know about this "G" Serial number type.
Good Hunting, kill cleans or just don't hunt.

Pete