I have several Mossberg 500s;  two of them have a small gap at the end of the magazine tube where the barrel support screws in.  Seems to me the barrel support lug should be pushed (as you screw in the screw) all the way flush with the magazine tube.

Does this matter? Is there any way to fix it?  There is no obvious damage or dents, both guns are in pretty good condition.  Looking at the barrel in the receiver end it's all the way in.  

Looks like the ejector might be able to be loosened and moved back a hair to let the barrel seat in more deeply to the receiver??

When you have everything together does it feel loose?  Is there any movement with the barrel once it is on and tightened down?

Quoted: When you have everything together does it feel loose?  Is there any movement with the barrel once it is on and tightened down?

No, everything feels nice and tight; zero play of the barrel and magazine tube; the screw is tight.

hello. this is normal on most mossbergs. i have over 14 mossberg pums and quite a few of them have this gap. if i switch barrels from one gun to another, sometimes the gap dissapears and sometimes it stays the same. i would suspect this is due to varrying tolerances in the barrels and the threading of the magazine tube. this doesnt affect the function of the gun at all. kirk

Quoted: hello. this is normal on most mossbergs. i have over 14 mossberg pums and quite a few of them have this gap. if i switch barrels from one gun to another, sometimes the gap dissapears and sometimes it stays the same. i would suspect this is due to varrying tolerances in the barrels and the threading of the magazine tube. this doesnt affect the function of the gun at all. kirk

Thanks that makes me feel better because ... well it's a long story but I got two fairly good condition mossbergs and had to swap the barrels and magazine tubes.  Anyway, after switching, BOTH had this small gap.. I can't explain it- because if one magazine tube was too short, it should have had the gap regardless of what gun it was on. I still can't figure it out.  I guess it doesn't matter though.
Has anyone ever asked Mossberg about it?

Like Kirk said, normal.