I had several posts about Mossberg 500/590 and was surprised by number of questions about this shotgun. First of all, I recommend checking infographic: Differences Between Remington 870 vs Mossberg 500 shotguns. It explains differences in controls and design. Mossberg 500/590 is a great and very popular shotgun. There are 10,000,000 of Mossberg 500/590 shotguns made to date.
So, this post is about the best and must have upgrades for Mossberg 500/590 shotguns.