Missouri church carry is banned. Not a felony, just a slap on the wrist and asked to leave. As with other "no carry" zones. But you can carry if you get approval from the presiding church authority.
I don't attend right now. I have some issues with the way things are going on with the churches in my area. But if I do start to attend again I will be carrying. "God don't care how you are dressed, He's just glad you showed up" If I like the church I will speak to the Pastor or Priest about carrying.
I'm Catholic by the way. I don't think a Catholic priest will have a problem with some one protecting the congregation, or the collection.:)