Some of these pistols loosen up like you describe. It really doesn't effect accuracy since the barrel and receiver are still rigid, but it isn't right. It sounds like bubba work but this is how I fix them. I put smooth jaws in my large bench vise and clamp the grip frame, upside down in the vise. Squeeze the grip frame so the "saddle" area gets a little narrower. This will increase the distance from the saddle to the dovetail that engages the receiver and tighten up the fit. Go easy, it is soft metal and will bend very easily. Better to take it in several small steps. The saddle ears could be peened with a small hammer but the vise is much more controllable.
