I think you may be missing the punctuation, common problem in old gun records.
I may be meant to read, 12 bore, top, bar, A&D, Ejector, 27" barrels, etc etc
In that case, I think JBG is correct but I am not sure what 'bar' refers to unless the action incorporates an unusual bolting mechanism such as the S Mills top slide but I think that is unlikely given the late date of the gun. Post 1920's actions had become pretty generic.