While no-one will accuse them of being fancy, the Mossberg 500 is an old and proven design, so I would not rush out and dump it because one brand of shells would not eject. Locate a gunsmith who does shotgun work, explain the difficulty to him and get his recommendation. Perhaps the ejection port could be opened up slightly, perhaps there is a problem with the ejector, perhaps simply switching brands of ammo will correct the problem. We all want our guns to perform flawlessly, and in the case of a 12 gauge pump gun, it should handle any commercial ammo you can throw at it. The problem is likely a minor one, and the fix inexpensive.