My custom Colerain .54 caliber swamped barrel is a 1-56 twist. They feel that is the roundball twist for that caliber. Larger calibers they tend to go 1-66 twist. For instance if I go to a .62 caliber Colerain it will have a 1-66.

Now if I had gone with a Rice barrel it would have been made with a 1-66 twist. So its hard to say what twist you should go with. Only you can decide that.