Mossberg 500, 20 gauge is nice, 12 is more versatile.
If you’ look and are fortunate, you can find those shortie rounds from Federal or Aquila.
No need to spend a lot on something you hopefully won’t need to use.
If you don’t know what the shorties are:
https://www.federalpremium.com/shotshell/federal-target/shorty-shotshell/11-SH129+8.html
I have a Mossberg 500. When I went sporting clays shooting with it (yeah, I know - 18” bbl), it wouldn’t cycle the short-brass trap rounds. The work around was to depress the release button next to the trigger.