I bought a beautiful 19-4 2 weeks ago for $500. It is very nice and locks up tight. I did notice that when the crane is open the cylinder can move back and forth about 1/16" but when closed it doesn't move much at all. I did notice that the inside of the barrel has a copper colr at the bottom of the rifling. What can be used to clean the bore for copper removal safely on a nickel gun? Or should I just shoot it? I only put cast bullets through all of my guns but I bet this gun has fired jacketed bullets.