The English call it a loop no matter what type or shape . No point in making up words when there is one in use that every one uses. The British trade uses a number of archaic terms such as tail pipe to refer to a metal forend tip ,hammers as well as tumblers in boxlocks ,older engravers talked of "back ends " instead of trigger guard tangs ,pins and nails as in breech pin ,hand pin or side nail , rather than screws . there are others but even some of these are now going out of common use .