The competition is called the "BFTA Constructors and Associated Trades Championship"
Rule 3 states:
Rifles and/or other equipment used by each team should come from the normal range of goods produced by a constructor and must be as close to "standard" as possible. We should all bear in mind that this is a light-hearted supplementary competition and the sole aim is to further the development of Field Target shooting.
Hope that helps to clarify.