Too many people associate a " leaded " barrel with only a problem with the cylinder throats . The throats are too small---yup there's the problem . Cylinder throats too large --- yup there's the problem .
Stop looking for just the " easy " fix , ream out the throats if too small or get mad at S&W , claim the problem is oversize throats and send it back to the factory . Gentlemen , there's more to it than that . I learned from the best , Veral Smith @ LBT Molds . I bought his little book , corresponded with him several times . Veral has forgotten more than most will ever know on the subject of shooting cast bullets successfully in revolvers , pistols and yes , even rifles . Everything that I read and he told me I found to be true . I had several with tight spots where the barrel threads onto the frame . I had to use a mallet to get the slug past that spot . I found tight spots where they roll stamped the barrel with markings , I had rough spots in the barrel from machine marks . Driving a lead slug slowly down a barrel , you can feel all of the above , if present . Those area's effect a barrels performance , leading / and or accuracy .
You can disagree / bash me all you want . But at the end of the day my revolvers shoot just fine and I've never changed out a cylinder claiming oversize throats . Do yours shoot satisfactorily ?