sounds like the rivets where bucked against the barrel this is the only reason iv seen a loose trunnion..... the proper why to install a front trunnion is to remove the barrrel support the back side of the rivet and then crush it properly..... this also lets u insure the rivet's mushroomed properly (not saying it was done this way but it is a good possilbilty) rearguard less it need to be addressed for safe operation