So my P80 build has gone relatively smooth, just cutting, filing, and sanding. But I've run into a literal snag with the U cut out on the frame and the recoil spring. When I got to put the slide on it feels like the recoil spring assembly is getting caught in the U. Should the assembly move freely with little resistance in the cut out? Just don't want to over do the filing. Sorry if this is a painfully obvious question.