[oldscot3]

With a little further research, I learned that some were m500s and some 590s. Apparently, 590s have barrels with heavier walls, better extractors, high cap mag s, etc., etc.

That's all part of it I guess, apparently the m500s just aren't as heavy duty.

edit: apparently only the 590a1 has a heavy wall barrel. It also has a alloy trigger guard and safety, other than that it's the same (I think) as a 590.