I have a problem with the term “sacrament”, in that it suggests a means for making Christ objectively “present”. I also have a problem with “ordinance”, because it suggests something merely expressive, rather than effectual and transformative. Regarding the Lord’s Supper, the issue is how and in what manner does Christ become present.
I think it best to say that He is always fully objectively and ontologically present. What is special about the Lord’s Supper is that it is a means for Him to become subjectively and psychologically present – for us to acknowledge Him, by remembering Him. It is a means of relational engagement, for us to become responsive to the One who is always there, who is always available. God has already done everything possible for reconciliation. The remaining relational deficiency is totally within us. It is a subjective deficiency, requiring a subjective solution. The purpose of the Lord’s Supper is therefore to make Christ subjectively present.
In this sense, it is an ordinance, but it is an effectual ordinance. When we draw near to Him, He draws near to us (Jas. 4:8). This is the main point of the Lord’s Supper, as well as baptism, and all other forms of worship. I think it best then to regard the Lord’s Supper, and baptism, as dramatic prayers, by which we draw near. These may therefore be regarded as “sacraments” in that they are truly effectual — but effectual in the same way that prayer is effectual, no more and no less.