I would avoid newer 870ís and Mossbergs both. They both have issues.
There has been something like 11 million 870ís made. Find a used one made before Remington was bought by Freedom Group. I have two, and theyíre solid guns.
Ive had several mossbergs, they donít have many issues that Iíve seen. Mine have been great. My best shooting shotgun was a maverick 88. Really wish I hadnít sold it. Killed A LOT of birds with that baby.