Define Decent Auto - I shot 3 gun - Remington 1100 was what I tried as I had friends that shot trap and they liked it (but they kept multiple one for match one for in for repairs due to heavy use), buy the time you get a mag extention, plastic fantastic stock and few other mod's your spending way more than a 870.
I saw guys trying to run the AK variants in 12 ga - very ammo sensitive. Only 3,5 and 8 shot magazines were run in matches - maybe one of the drums when starting but no one I saw carried a second drum to reload with.
Some (wealthier) shooters ran Benelli's which ran well, but I can't see this for a new shooter at $1,500+.