I don't know if this question has been asked before but does anyone know if Mossberg has redesigned their plastic trigger group and beefed them up or they have always been the same ?
To my knowledge, only the 590 had a metal trigger guard. Even the first runs of 500's that I'm aware of were plastic. I've seen some easily dating back to the late 60's or early 70's and they were all plastic guards.
midwyusa and ebay and numrich could probably be decent sources to maybe find a metal one if you're looking.