As a side note, the High Standard only had one action bar IIRC. Generally two is considered better although I never had an issue. I don't know about the others you listed. The 870s I've had experience with all had two action bars. The 870s were the first riot guns I was issued at other agencies I worked at and they were always good to me too. Being an economy model the Maverick may only have one although I think most Mossbergs have two.
Savage was one action bar as I recall. Been many years since I had one.