Unless it's caused by deep gouges in the chamber, the sticking is a high pressure sign for that chamber, meaning your load is too hot for it. You didn't say what load you are shooting. If it is one of those "Ruger only" warmer-than-standard loads, then I expect the chamber is either too large, as Weshoots said, or the cylinder moved during drilling so that chamber is slightly out of place toward the outside. Either will make the steel too thin. I suppose local heat treatment failure is also a remote possibility, but pretty unlikely.
Whatever the cause, there is a physical problem with the chamber that simple reaming is unlikely to fix. Even if it were gouges that reaming could fix, Ruger will probably do it free of charge. They're not quick, but they put a factory finish on inside and out when they're done, which is nicer that the cold blue from most shop work on chambers. Let Ruger have it.