I have a 590A1 20" barrel, 8+1 cap. The A1 is important. It is the heavy military shotgun. NOT the same as a regular 590. That means it has a thicker(noticeably) barrel, metal trigger guard and safety button. The 590 and A1 both have the bayonet lug I believe as well. The 500 is a more cheapy-civilian version. No, I don't have a 500, but I've handled them at shows and it is just my opinion.