I have a 6 shot 617 4" that I have never had any problems with,however I recently bought a 63 4" that had hard extraction.i cleaned and cleaned some more all to no avail,finally I put some flitz on a mop and ran it on a drill for a few seconds on each chamber.I had been instructed to not take the mop too far into the chamber and was very careful to do this. I then made sure to flush out any residue,and now I have had no further problems.YMMV