When the slide is rearward, the only thing holding the barrel is the slide stop pin, thus it is loose and floppy - has to downlink so that the barrel throat aligns with the feed ramp so a cartridge can be fed. When the slide is forward the most favoured condition in a match tuned pistol is NO slop at either end, unfortunately in military trim there will be a small amount of play between barrel and bushing as well as between bushing and slide - at the rear the barrel may be able to be pushed down ten to twenty thou. If you run the slide forward, have the hammer cocked, the safety engaged and pull the trigger and shake it you will hear many pieces rattle. A match gun will be silent and no movement of internal parts will be perceptible.