I just bought a used 870 Wingmaster barrel, the barrel guide ring appears to be pushed backward. When attached to a receiver the ring is gap between the ring and the barrel but is uneven. It is open at the bottom like the ring was pushed back..
A new barrel ring is only 10.00 at midway but I don't know if I should/could replace it.
Anybody ever dealt w this..

Can you see any cracks or damage to the area where the ring is brazed to the barrel?  The ring may stay attached forever or it may break loose on the next shot, just no way to know (and if it breaks loose the barrel can come off when fired).  

To properly repair that part the ring will need to removed, realigned correctly and re-brazed. The metal finish will be affected. At retail the cost for all that may end up being more than a new barrel

If you find no damage to the brazed area its possible that the surface of the ring is just not square with the bore and magazine tube. (Remington QC sometime leaves something to be desired )

How wide is that gap? Could be just a cosmetic issue...