I'm not exactly sure I know what part you are referring to, but if it is the barrel lug, the part that attaches under the barrel that the wedge pin slides through after the barrel is on the stock to hold the barrel on the stock, use a punch and put a dimple on the barrel side of the part, and put it back. That should tighten it up. That's what they say to do when putting a kit rifle together if the barrel lug is loose.