I gotcha... and I see you are right. The plastic nut is readily available and so is the spring, but the 457 catch itself seems to be hard to come by. Over on the blue forum, there's a thread or two about using a 4506 catch and nut on a 457 and you can apparently do it without modifying the 457 frame for the plunger. Instead, you locktight the nut on so it doesn't spin off. Have you considered that approach?I am not sure about any of that.. I am looking for original S&W 457 parts or an known fix for the Magazine Catch wear/failure.